Stellvia of the Universe is set in such a world. Except for the civil unrest, the quiet hints of xenophobia.. The point is that humans are capable of this given a unifying factor such as the second wave, but go right back to causing trouble without one. Besides, who was it went and deployed children in combat craft without any need for preparation?
The planet Aqua (Mars after extensive terraforming) in ARIA plays the trope straight.
Although it's not seen, since the story happens in the beginning of the second War Games, this is supposedly the reason that the Chess of MÄR began their campaign seven years ago.
Subverted in the Mobile Suit Gundam Wing side story "Battlefield of Pacifists," in which the actual name of the antagonists is the Perfect Peace People. It turns out their idea is peace is policing the now (mostly) demilitarized Earth Sphere by acquiring all remaining war machines for their own use.
In Tripeace (named after a group dedicated to ending war forever) there was a certain small country that did away with weapons and violence and lived peacefully for many years. After they were annihilated by an enemy country the survivors formed the terrorist group Ares (or Hades) and dedicated themselves to causing conflicts to avenge the destruction of their country and because "war is eternal".
The people of Zenn-La, the homeworld of the Silver Surfer, became this during their Golden Age of Reason. They had a single 'ultimate weapon' of such 'terrible' power that they were certain if a threat came along that required deploying it it would defend them against all threats (since they were after all the pinnacle of perfection). Galactus didn't even appear to notice its deployment as it didn't even slow his ship down. At which point they were helpless as they'd put all their defensive eggs in one basket.
According to the first issue of Marvel's Transformers comic book series, the original Transformers were such a society. Megatron creates the Decepticons out of disgust at their satisfied lives, and the Autobots learned to fight back by copying their example. This origin was Ret Conned away in later stories.
In ElfQuest, The Sun Folk are like this for much of their history before the Wolfriders joined them, confident no invader would ever make through the desert to reach them. Leetah, their powerful healer, eventually realizes that she made this situation worse by taking care of the slightest medical problem immediately and thus made her people a bunch of wimps. However, when things start getting more dangerous, they willingly accept combat training in order to defend themselves.
The Wosk in Atavar sealed themselves off from the rest of the galaxy to avoid war, and when threatened by the UOS, decided to pray instead of fighting. Too bad their god turned out to be galactic cancer aiming to wipe out all life.
In The Last Starfighter, the Star League is so devoted to pacifism that when they are threatened by the Ko-Dan, they could only find a few dozen members from all of their member planets with sufficient bloodlust to become Gunstar gunners. In desperation, Centauri searches barbarian worlds outside the league (such as Earth) for others with the ferocity and skill they needed. This was especially evident in the Novelization, where the mere mention of physical violence made many League members uneasy.
Star Trek: Insurrection has the Ba'ku, who refuse to fight even when they discover that invaders are trying to forcibly relocate them off their tranquil planet. Their leader even says "The moment we pick up a weapon, we become one of them."
Although that reluctance may not be solely a result of Perfect Pacifism, so much as a result of some of the invaders being their own children.
The Amish in Witness. A notable scene features an able-bodied young Amish man refusing to fight back when some tourists smear him with ice cream, prompting Harrison Ford to deliver an ass-whuppin' in his stead. Despite the fact that Ford uses violence to take on the villains in the climax, the Amish actually use their nonviolence to defeat the final villain by witnessing his evil actions. Even though they won't fight him, there are simply too many of them to kill, so he's already lost.
In A New Hope, Princess Leia pleads that the people of Alderaan are this. It doesn't sway Grand Moff Tarkin. In the Star Wars Expanded Universe novel The Bacta War, one expatriate Alderaanian, now a starfighter pilot for the New Republic, ponders the implications of such a society. He concludes by finding himself disagreeing with the idea:
Wrapped up in it's cocoon of pacifism, Alderaan had seemed insulated from things going on in the galaxy. It was as if when we disarmed we set ourselves above the petty concerns of the galaxy, and we thought doing so would keep us safe. ... He had long since seen the error of that philosophy. Pacifism for the sake of pacifism is the height of arrogant selfishness when that belief prevents you from acting to save others from harm.
The Krell in Forbidden Planet are referenced as having moved to this point, at least until their psychic monsters were unleashed.
The Day the Earth Stood Still (1951) has a version of this. Klaatu says that his people live in peace and are free from aggression and war because of the creation of the Gorts and giving them absolute, irrevocable power over the people.
Planet Tenara from the Star Trek novel "Captains' Honor" is a perfect example, as the people have long renounced violence (the last murder was 30 years ago). When they are attacked by the M'Dok, they must either re-learn violence or get slaughtered. And then an overzealous captainjumps off the slippery slope...
A Door into Ocean by Joan Slonczewski have a race called the Sharers, Actual Pacifists who use genetic engineering to manage their world's ecology. When traders and soldiers threaten their world, they have to repel the invaders without compromising their pacifism.
The Time Machine plays this trope straight, but with a twist. While the Eloi truly are pacifists living a life of automated luxury, it's only because they're livestock being herded by the Morlocks.
They've also been trained and genetically selected for these traits. Anyone who fights back is killed and taken first... not only setting an example to the others, but removing more naturally aggressive specimens from the gene pool.
At the time of the First Contact with the Kzin in the short story "The Warriors", humanity has been conditioned by the A.R.M., basically benevolent Secret Police who rule Earth with a soft but tight iron grip backed up by Government Drug Enforcement, to totally reject war and physical conflict. When word gets back to Earth about the Kzin first contact, this comes to a rather abrupt end, and soon thereafter the Kzin find out exactly why humanity gave up war.
The Pierson's Puppeteers are like this, but not because of idealism; rather, cowardice is their hat, and they almost never attack openly for fear of retribution (except Nessus, who's the Puppeteer equivalent of Ax-Crazy). Their other hat, however, is Manipulative Bastard, so they find other ways to defend themselves. One semi-canon offshoot novel by a different author implies that they once had a protective Proud Warrior Race Guy caste, but they have not been seen in the main continuity and are implied to be rare nowadays anyway.
Uglies, by Scott Westerfeld, gives us the "Prettytime," in which everyone is sweet-tempered and a little bit lazy. This is because after the operation, everyone gets brain lesions. So it gets played with somewhat.
Animorphs has the Pemalites, a ridiculously peaceful race who were completely obliterated by a more militaristic species. Tragically, their incredible technology could have been converted into weapons that would easily destroy their opponent, but as a species they couldn't bear to do so.
Said technology lives on in the form of the equally pacifistic Chee, a robotic "race" created by the Pemalites, dog-like in their natural state but able to project an image of being human. Their programming doesn't allow them to be violent.
Animorphs also has the Hork-Bajir, who while not as advanced, were also totally peaceful, and were enslaved when they caught the attention of a more aggressive race. Notable in that all of these species were created artificially, and designed to be non-violent by their creators. The series seems to give the impression that while being a pacifist sounds great, in reality it isn't a good survival tactic.
Deconstructed by the Bandakar society in the Sword of Truth series. Exiled beyond a magical boundary for being pristinely ungifted, they adapted by forming a near-unbreakable community bond, going so far as to outlaw any form of violence against each other. The deconstruction comes when the heroes find out that their pacifist philosophy extends even to self-defense in any form. Deviant criminals who've committed murder are attempted to be rehabilitated several times beyond the point of common sense. As a last measure, they subdue the offender and dump him down a cliff that leads outside the boundary as a form of exile. They won't attack or drive off predatory birds that occasionally fly off with young children. And when the Imperial Order comes to call, the most they offer is a meek protest when its soldiers proceed to kidnap and rape women of all ages in a program of systematic breeding to cultivate their ungifted trait. Even when the heroes attempt to train them to fight back, the Bandakarans mostly refuse, saying they have no right to judge the men of the Order as they don't know the circumstances under which they're acting. And then the heroes slaughter them.
"Pacifist's War Song," a poem by H.P. Lovecraft. They're cowardly, effeminate, and proud of it.
Piers Anthony's Macroscope is about an interstellar communication network that destroys the mind of anyone else. Turns out it was a safety feature - any other race would use the knowledge to wage an interstellar war.
This is what the Capped humans always said the Masters helped humans achieve in the The Tripods series. And it's true, it's just done by mind control that makes humans docile, and apparently unable to maintain any technology beyond medieval/renaisance age.
The Tuatha'an, Traveling People, in The Wheel of Time are a race of nomadic Actual Pacifists who call their philosophy the Way of the Leaf, because a leaf does not resist force but is blown as the wind wills. Other than their pacifism, they are closely based on real-life Irish Travellers, in culture and in name- 'Tuatha'an' is derived from Old Irish and both groups are commonly derogated as Tinkers. Like their real-life counterparts, the People are seldom welcome wherever they go, but in this setting it's because their outlook is so idealistic that it tends to attract young people to join them. The People spend most of the books being slaughtered, both by the agents of the Shadow, and by prejudiced human neighbors.
Several species in Star Trek feature races and societies with this trope to varying degrees:
Vulcans embrace logic and pacifism to the point of following strict vegetarian diets. They're willing to incapacitate intruders with non-violentmeans, however.
Whille the Vulcans are usually characterised this way (complete with Cultural Posturing), they still seem happy enough to serve Starfleet in a military capacity when required, and even maintain a small fleet of their own warships.
Though the Romulans (or at least Sela) seemed to think that 4 warbirds would be enough to conquer Vulcan, so they can't be that militaristic (or the Romulans wildly underestimate them, which is also possible).
The Halkans are a society with a history of complete peace; they are so devoutly pacifist that they refused to allow the Federation to mine dilithium from their planet for fear that it would eventually used for violent acts.
The Grazerite are a bovine-humanoid species who advocate community and pacifism.
The Aenar have a strictly pacifist ideology and deplore violence.
The Mizarians, a race that embraces total and absolute pacifism. They've also been conquered by other species six times over the course of three centuries. Apparently they survived by offering absolutely no resistance until, one assumes, their conquerors simply got bored and went elsewhere, or their conquerors got conquered by someone else.
The Organians. Pacifism is easy when you're a race of immortal Energy Beings several magnitudes more powerful than any would be invaders.
Subverted in "A Taste of Armageddon": The people of Eminiar (and the neighboring planet) have fought their war so long that they stopped using weapons lest the war destroy both civilizations; instead, computers simulate attacks and the designated casualties report to convenient booths for routine disintegration. Their aversion to weapons does not keep them from using deadly force against the Enterprise, but does frighten them into opening communications and peace talks when their war computers are destroyed.
The natives of the planet Neural in "A Private Little War" were pacifists, until the Klingons start arming some of them, and Kirk decides to arm the others to even things up.
A race of telepaths encountered by the Voyager has outlawed violent thought in order to protect society from unintentional violence. Unfortunately, they forget to tell this to their visitors, resulting in B'Elanna (a fiery half-Klingon) "infecting" a passerby with a violent thought (it's later discovered that he is from an underground community who sell violent thoughts and specifically provoked B'Elanna. A few minutes later, a local murders another local over a tiny disagreement due to the influence of B'Elanna's thoughts. She is arrested by the local police and sentenced to have her mind purged of violent thoughts. Realizing that there's very little to B'Elanna besides violent thoughts, the crew fights to prevent this.
Like the example of the Mizarians above, the episode "The God Complex" featured one tourist from a planet that had been conquered so many times, their entire culture had developed around surrendering without a fight. Their national anthem is "Glory to Insert Name Here," and at the time he was kidnapped he was working on a project to line the road leading into their capital with trees so that invading armies could march in the shade.
This trope was often denounced in contradiction to the show's common reputation as pacifistic. In particular, "The Daleks" has the Thals as helpless against the Daleks until Ian teaches them righteous anger, and "The Dominators" is an Author Tract about how pacifists are irresponsible cowards who will get deservedly slaughtered by the first non-pacifist culture to meet them.
Stargate SG-1 has the Nox, a highly advanced species disguised as simple naturalists. They refuse to participate in anything that may harm others, and won't even fight to defend themselves. Then again, they can cloak themselves and revive the dead. They also tend to get very snotty toward people who have every reason to be extremely wary and who literally have no other option other than to fight to survive. Oddly enough, the humans act as if the Nox are right to virtually condemn them.
In fact, the first Nox that SG-1 meets would have been killed if the humans had not fought to protect them. The Nox don't really acknowledge this, and still believe that fighting is unnecessary. But not all of them are quite completely pacifistic: one of them helps fight off a Goauld attack by cloaking a gun (she didn't fire the gun, so it didn't count as fighting), and of course the race is/was allies with some other advanced races who were definitely not pacifists.
The Furlings are implied to have met their end by becoming this sort of culture; they hid away in a secret location, intending to make it a peaceful utopia, and then they accidentally ate a hallucinogenic plant (possibly brought by one of the evil races) that made them all kill each other.
The Leviathans in Farscape were built as an enforced version of this trope: because they don't have any weapons and can't be modified to that end, most of them take the most diplomatic route possible- hence the reason why they're so easily enslaved. Plus, when Moya gave birth to an gunship, she narrowly avoided being decomissioned by the Builders, who refused to see their creations modified to violent ends.
An episode of Legend of the Seeker has the heroes happen upon a village of these, who are being raided by a local warlord. However, when Richard attempts to train a few volunteers how to fight, they go into a coma-like state. Zedd discovers that any attempt to cause violence is blocked by a spell case long ago by a powerful wizard. When Richard convinces him to lift the spell (despite Zedd's objections), they very quickly realize why the spell was there. The trained villagers develop a magically-fueled bloodlust resulting in a slaughter of a garrison of soldiers of the warlord, with Richard (who has succumbed to the same bloodlust), leading the assault. After the situation is resolved peacefully, Zedd explains that, long ago, an evil sorcerer bound a group of people to his will, giving them a bloodlust like no other. For their own good, a wizard put a spell on the people and their descendants that required them to abstain from violence. Oh, and that evil sorcerer is Richard's ancestor (a Rahl), which is why the berserk villagers were following him.
Wonder Woman: In this incarnation, Paradise Island’s amazons are this because they are a Proud Scholar Race. In contrast with the Proud Warrior Race from the comics, the amazons were overpowered by the Nazis in “The Feminum Mystique”. However, the Amazons easily overpower the Nazis once Wonder Woman and Wonder Girl came back to liberate the Isle.
On The A-Team, the team was once hired by a group of pacifists to protect them, but when the team tried to use violence, the pacifists fired them. Hannibal said that at least they weren't hypocrites.
Several alien races fit this mold in the background of Warhammer 40,000. Then the Imperium of Man encountered them, and those races no longer exist.
In the Mystara setting's Hollow World, a Hidden Elf Village is home to the Gentle Folk, elves so pacifistic that they were wiped out on the surface. Not a utopian example, as their extreme passivity and reluctance to impose their will on others makes them rather depressing company.
The Liir from Sword of the Stars, empaths who feel the pain of others. They depend on a caste of voluntary Ax-Crazy Liir for defense.
Subverted somewhat in that they have no concept of military restraint - they see no essential difference between firing a warning shot and wiping out every creature on every world of an entire empire with horrific bio-weapons.
The Serenes people, a bird laguz tribe in the Tellius-Saga of Fire Emblem, not only tend to be extremely peaceful and pacifist, but also are practically incapable of physical violence and break their knuckles with even a simple punch. They also are very fragile and easily get sick. It is therefore no surprise that they were almost completely annihilated in the Serenes Massacre when they were falsely blamed for a murder. Subverted a bit since the last remaining herons show to have become a lot tougher in spirit and less pacifistic, although they still cannot fight on their own. It is also mentioned that there are forbidden songs that can cause considerable damage, though performing them warps the singer in some way. Subverted further by herons who have lost their powers by having a child with a beorc and the resulting half-herons. Both groups make very powerful magic users.
Your faction can eventually get to this point in Sid Meier’s Alpha Centauri, once you develop Eudaimonia civic. As Encyclopedia Exposita explains, Eudaimonic society is tolerant and just, and even when it has to go to war, it prefers to subdue rather than kill. In game mechanics, it means lowered morale of military units.
The world government in Hostile Waters has used Nano Machines to remove poverty and need, effectively removing all reasons to go to war. This brought along with it a paradigm shift in the way people viewed the world, creating a peaceful world. The player controls the last warship on Earth, beating down a piece of The Remnant that has re-surfaced and is planning to bring it all down again.
In the year 2012, the Earth was hit by the last thing it was expecting: Sanity. 2012 was the End of Days in the old Mayan calendar, a time of great change, the conclusion of history, and it seemed to coincide with a great sea change in the way people saw the world. No-one dared suggest that it brought the change with it, of course. But suddenly, we all looked at each other, and saw not where we all came from, but where we were all going. And we decided to all go there together. This is what we are fighting for. This is what the old rulers don't want us to have. A world gone sane.
The bird-like Chozo race from Metroid are Precursors who have evolved to a point in which they live in harmony with nature, shunning violence and destructive technology. Of course, they were warriors once, and were able to create the advanced Powered Armor that Samus uses. The downside of this is explored as well: after being pacifists for so long they could no longer use their own weapons even when they REALLY needed them.
Ōkami has the Celestials, a race of angelic (they have wings on their head) beings that were driven into extinction by Orochi and his Demons. Some of their ghosts appear in the game.
The Dimension of Lame from Sluggy Freelance, who find food fighting to be immoral and voluntarily heal the Demonic Invaders who are enslaving them and eating their souls. Their greatest weapon is a warhead that dumps millions of "Please don't kill us!" notes on a city. They subvert the Training the Peaceful Villagers trope as even with weeks of training, they still cannot comprehend violence enough to deliver a single hit to a demon without bursting into tears. The only reason they survived to the end of the arc is due to their sheer numbers tiring the demons out.
Bravestarr: The sheep-like humanoid Foofta aliens, from the episode "The Ballad of Sarah Jane", are these with a dash of Space Amish. When Bravestarr saves them from being enslaved by the Krang, their leader is so horrified by the use of any sort of "violence" that he threatens to turn himself and all his people over to the Krang.
The Air Nomads from Avatar: The Last Airbender were a great example of this, having no army and preaching peace and harmony. That is, until the Fire Nation killed them all save one boy. Not that they went down without a fight. The skeleton of the hero's mentor, Monk Gyatso, was found surrounded by a dozen dead soldiers. Keep in mind, Gyatso killed those soldiers when they had each been empowered by a passing comet with the strength of one hundred firebenders. And Avatar Aang himself, although he had a strict No Killing policy, never showed an aversion to fighting or harming people.
The episode "Defenders of Peace" had the Lurmen, a group of rural villagers who refuse (by will of their elder/leader) to align with either the Jedi or the Separatists, even when threatened with a Separatist bioweapon. A few of the younger Lurmen side with the Jedi when the village is under attack.
The Mandalorians under Duchess Satine, Madalore remained neutral in the Clone Wars and maintains a peaceful society under her rule. But it all starts going under fast when Death Watch and Darth Maul easily overthrew her puny regime in an orchestrated False Flag Operation which makes Death Watch look like heroes.
The Moriori people of the Chatham Islands were pretty close to this, an utterly pacifist society of hunter/ gatherers. When a Māori invasion came in 1835 they didn't even understand the concept of armed conflict and were almost entirely wiped out as they tried to negotiate. The invading Māori killed, enslaved and cannibalised the Moriori, although Moriori culture has since received a Renaissance in recent years.
Quakers. Being a Quaker is one of only a few ways you can get out of the draft. William Penn founded Pennsylvania on the basis of Quaker-style pacifism. Before the U.S.A.'s independence Pennsylvania had no militia and only a tiny police force. Though religious freedom in the colony meant that not everybody was a Quaker and subsequently it didn't go entirely to plan. Pennsylvania did have a militia formed by the non-Quaker immigrants, who often expressed resentment at the founders of the colony, who from their perspective did not pull their weight in ensuring the safety of the colonists. Whether Pennsylvania would have survived unmolested without them is a subject of some degree of debate up to this day.
There are many religious and secular movements which are at least anti-war if not completely anti-violence. As with philosophies in general the behaviors of individual members and the level of adherence can vary dramatically.
Bonobos, a species of great ape, are much, much more cooperative and non-aggressive than their chimpanzee cousins, or indeed any other social primate. They instinctively settle disagreements with sex rather than violence.
Anime and Manga
One Mobile Suit Gundam Wing sidestory has a subversion with the so-called Perfect Peace People. Despite all their constant rhetoric about how pacifist they are they are little more than terrorists who brainwash people and use violence to enforce their peace.
Deeply, deeply subverted in Texhnolyze. The Theonormals who inhabit Earth's surface exiled everybody with genetic tendency towards violence underground, and created a utopian society free of fear. As a result the said society became horribly stagnant, losing all passions and interest to do anything but remniscence the old days. Even the threat of the exiles returning to slaughter them all fails to provoke any reaction beyond "that's nice".
The Alliance tried to create a world like this artificially in Serenity, for the most part it worked a little too well - but also ended up creating the Reavers.
Gulliver's Travels has the Houyhnhnms, a race of sapient horses that Gulliver encounters that at first appears to be this trope played straight, (until they get the bright idea of driving the Yahoos to extinction via castration) They lack many common human vices and so have no words for them in their language and have to resort to roundabout euphemisms to describe them, e.g. "to lie" becomes "to say a thing which is not".
This Perfect Day starts with a utopia without poverty, hunger, violence, or fear. It turns out this is because everyone is drugged and genetically engineered to behave this way, controlled by a supercomputer that is controlled by a cabal of immortal programmers who live in true luxury.
Zigzagged in the Confederation of Valor series. In the backstory it's justified: for the most part only species that evolve past violence achieve Faster-Than-Light Travel, because species that don't have a tendency to blow themselves up first. Deconstructed when the Others show up and begin attacking, and the Confederation has to uplift first humanity, then the Taykans, Krai, and Silsviss because they haven't evolved past violence. Arguably reconstructed as of the latest books. The war turned out to be a giant sociology experiment by Sufficiently Advanced Aliens operating under Blue and Orange Morality, and it seems highly likely the Others have the same arrangement as the Confederation.
As seen in The Forerunner Saga, the Forerunners are slow to anger. However, when it's apparent that their people, planets, or religious beliefs are in danger, they go to war with an unstoppable, efficient brutality. They will wipe nearly all traces of the offending civilization from existence if need be.
In Vorkosigan Saga the Betans might want to be thought of as this. However they are capable of interfering with their neighbors quarrels admittedly on a perfectly justifiable occasion like the Escobar war. What is more to the point is that they are arms dealers which makes them hypocrites when they condemn other people's bloodthirstyness.
The Quaddies are closer to the straight example. However though they would not be capable of resisting a determined attack they have no qualms about using force to defend themselves.
The Shin in The Stormlight Archive maintain their pacifism simply and efficiently: Anyone in their culture who takes up arms is instantly enslaved for the rest of their life, traded around as a mercenary fighter. These "Truthless" are rare, and tend to get killed quickly.
Dying of the Light: The planet of Kimdiss is presented as this by Arkin Ruark, who as a Kimdissi is utterly disgusted by the barbaric ways of High Kavalaan. As it turns out, Arkin is one of the main antagonists of the story, and Kimdiss' nonviolence is more the result of manipulation than pacifism. The bad blood between them and High Kavalaan is their own doing: the Kavalar had once upon a time joined into a confederation before the Kimdissi, fearing an united planet, incited a civil war.
The Federation in Star Trek claims to be one of these (among themselves), though they're not above keeping their "exploration vessels" well-armed... just in case they encounter any unenlightened races, of course.
Given that The Federation has plenty of war on its frontiers one might wonder if it has really achieved more then an interstellar version of a Pax Romana. Which may be something to be proud of from some points of view but is hardly Pacifist. But as the good Squire said in the episode The Squire of Gothos , "That's the official story".
It should also be noted that Star Fleet is explicitly supposed to be a military organization, at least in several parts of the Star Trek timeline (most notably the Original Series and Deep Space Nine).
The Angosians of TNG eschewed violence for intellectual development. When threatened by the Tarsian War, they genetically engineered some of their citizens into Super Soldiers. Since the treatment was irreversible, war veterans were confined to a penal settlement.
The Metrons are an isolationist race who shunned violence; they stopped a conflict by transporting Captain Kirk and a Gorn captain to a nearby world to settle their dispute, without the permission of either. After Kirk spared the Gorn, the Metrons offered to destroy the ship of the loser and then suggest that humanity may become civilized enough to warrant their attention in several thousand years. Given that that sort of thing sounds like simply a sufficiently advanced version of Captain Kirkian Gunboat Diplomacy it is hard to tell how they were any different from The Federation except in power.
Another example of Cleaned Up for TV - in the original story (Arena by Fredric Brown) there's no quarter given or asked. The human wins and the alien society is destroyed. Of course we're the good guys so who cares. The story was published in 1944 so there's that
In Babylon 5, the Minbari homeworld is startlingly peaceful, despite the Minbari's warlike reputation offworld. In the 4th season, however, half truths galore are used to technically claim that they weren't actually killing one another during their civil war.
In Stargate SG-1 the Tollan seem to be this too, until Anubis shows up with enough firepower to get through their defences, and then their leaders turn out to be really quick to sell out everyone else in the galaxy, to save their own hides.
Not only that but they also arrange a "heart attack" for the one leader who would fight this decision.
In Banshee the local Amish are pacifists who refuse to fight people who attack them. However, most of the local toughs know that attacking the Amish is a very bad idea. Kai Proctor, the local crime kingpin, comes from a prominent Amish family. The Amish have disowned Proctor and are shunning him but he still insists on protecting them against any bullying or insults. When the Moody brothers forget this, Proctor delivers a No-Holds-Barred Beatdown to Cal Moody that ends in Cal missing most of his front teeth.
Asari play this trope up, responding with diplomatic measures to threats, but when that fails, they subvert it and send in the Asari Commando units. Lets just say, they can skin you alive... with their minds.
They also don't like to advertise the fact that many of them spend their youth adventuring the galaxy in mercenary bands for kicks, but it's certainly no secret. Mass Effect 2 shows this side of the asari much more than the first game, as well as introducing the Knight TemplarWarrior Monk asari Justicars, who enforce the law in asari space, usually with violence. Not so pacifist or perfect as they seem.
The sequel also introduces the Ardat-Yakshi, which subvert the Green-Skinned Space Babe idea by utterly destroying their mates, often becoming megalomaniacs in the process and playing up themselves as gods. The Justicar in question specifically states that asari prefer not to talk about them because they like being thought of as the ultimate diplomats.
Well, they still are the ultimate diplomats. That just means that they are also the ultimate manipulators, and when they go bad, the ultimate emotional abusers.
It's mentioned offhand in Mass Effect 3 that a race in the previous cycle, called the Synril, claimed to have found the path to becoming perfect pacifist people. It's unknown if their plan would have actually worked because the synril got wiped out by a much more violent race called the ditakur.
Supreme Commander. The Aeon Illuminate are this on the surface, being a theocratic society based on tolerance, forgiveness, and love, but one thousand years of war have seen many Aeon turn that doctrine on its head: quasi-telepathic empathy and understanding of another person means you can predict them and know how to kill them, with the result that the Aeon are seen as Scary Dogmatic Humans by the galaxy. The Aeon civilian leadership hopes to return their society to Perfect Pacifist People, though.
In Infinite Space, one such civilization is met by the flagship bearing Galactic Conqueror Emperor Taranis of Lugovalos, greeting his declaration of impending conquest amicably yet professing that they have no desire for war. He genocides them on the spot. The Lugovalos are usually happy to absorb most conquered civilizations into their own without excessive tyranny, but Taranis sees no worth whatsoever in people who forgot how to defend themselves.
The Goner fringe sect in the X-Universe series are normally Actual Pacifists. Their ships don't have any weapons mounts at all, in contrast to every other ship in the game apart from cargo drones. However if pushed hard enough, they will fight back with lethal force: the climax of the Goner plot in X3: Terran Conflict consists of smuggling a bomb onto a Space Pirate station whose denizens have been beating the crap out of the supply lines to the Goners' new headquarters.
The Journeyman Project starts out after World War III, subverting this trope. While Earth is unified and all borders are dropped by the present year, 2318, time has been altered so that this no longer happens. The player, therefore, must fix this.
Homestuck: Beforan society was apparently the total opposite of Alternia - it was totally peaceful and the caste system was even reversed so that the higher castes are expected to take care of the lower castes. However, there still is a caste system, and an imperfect one at that, and while outright violence is uncommon there are just as many if not more Jerkasses among the Beforan trolls as the Alternian ones.
The spartan theme society from the Samurai Jack's 300 homage, as they describe their society as calm, pacifist and prosperous, but their army had to go to the war in order to defend their home from mechanical minotaurs. On the other hand the civilization never stopped to be an utopia thanks to their soldiers.