Hitler gets a cameo in the Fullmetal Alchemist movie. He never speaks well, almost, but the camera constantly pans to his eyes, which have a mad, manic glare that gives the impression that he's constantly about to snap and kill everybody around him. There is a slight chance of double standard here, given what the primary Fullmetal Alchemist universe is like.
While it's very doubtful he could ever try to kill anyone in a hand-to-hand way in Real Life, it's not like he never did shriek or roll on the floor and bite a carpet; he was dosed up on all kinds of stimulants and psychoactive "vitamin" regiments by his Crazy Nazi Scientist doctors...
Those happened in his later days, however, when his sanity was seriously slipping. His appearance in Fullmetal Alchemist is before he gained power, when he was just a leader of a small extremist party, and was a lot more charismatic and still had at least a good semblance of sanity despite of his hard-lined politics.
Hitler really did act like that when making speeches, at least on some occasions. Yes, he was charismatic, but his message was one of furious anger at the state Germany had fallen into; manic energy and passion were part of his performance. He didn't look like he was about to kill everyone around him, he looked like he was on the verge of storming out and leading his "army" of followers to overthrow the "corrupt" Weimar democracy and restore Germany's honour. Its nothing to do with his sanity slippage later on in the war (and make no mistake- he was not a sane man even in these early days) and everything to do with the nature of the speeches he made.
Invoked in Code Geass with a character getting himself basically nicknamed "Lelouch the Demon".
Cerebus does this to the entire female gender for the last third or so of its run (very arguably earlier).
Elf/human relations in ElfQuest are traditionally prone to this as the humans tend to try to fit the elves into their own pre-existing belief systems as supernatural beings. Which means that elf tribes who aren't lucky enough to hit it off very well with their human neighbors right away tend to get quickly labeled 'tricksters' and 'evil spirits'.
Admittedly, the Wolfriders have a tendency to make this reputation for themselves in their early history, when harassing humans was something they did for fun.
There is a Naruto fanfic known as "Naruto Veangance Revelaitons" [sic] that demonizes religious people, homosexuals (or at least male homosexuals), and people who like modern music.
Sometimes someone resorts to Demonization in an admirable attempt-gone-horribly-wrong to fix someone else's Demonization, as a case of He Or She Who Fights Monsters. For example, the fanfic author known as Cori Falls was motivated to write most of her works in response to her frustration that Team Rocket kept getting demonized, in her view. Unfortunately, she chose to attempt to fix this demonization by demonizing Ash Ketchum instead, and she demonized everyone who stood against Team Rocket in any way, which somewhat detracted from the quality of her fanfiction and thwarted her attempt to lionize Team Rocket.
As another example of "Demonization as a response to Demonization", someone wrote a fanfic called "Hogwarts Exposed", in which Hogwarts cheerfully embraced the practice of nudism, meaning everyone going around naked all the time. The fic was written as a response to the fact that most people demonize nudists as a pack of sexual perverts or irresponsible hedonists. But there were two problems to the author's attempt to fix this demonization: one, the fic demonizes everyone who hates nudism instead. And two, the fic portrays several of the nudists as sexual perverts only without actually criticizing their behavior, thus ironically destroying the point of defending nudism in the first place! An added layer of fail is added by the fact that nudism isn't routinely demonised in the country in which Hogwarts Exposed is theoretically set, as most people don't really give it much thought at all.
Morgan le Fay was a victim of this, since the publication of works which were often Older Than Print or Older Than Steam, like those postdating Chretien de Troyes's ones, all because, to sit well with his audience, a healer had to be A) a man B) a nun. She was only made ambiguous and ultimately good as of La Morte d'Arthur, but later works shew the woman who saved her brother by sending him to Avalon as a vengeful Vain Sorceress. Something which was partly kept up until some modern works like Marion Zimmer Bradley's modern novel The Mists of Avalon.
Sword of Truth does this simultaneously to communism and theism by having the main villains of the series be an evil empire set out to conquer all of the world and force their fundamentalist religion and bureaucratic soviet economy upon it.
Paradise Lost does this the most literal way possible, identifying the gods from the other religions of the ancient Levant as higher ranked of Satan.
The In Death series: Defense attorneys tend be subjected to this. Then again, the story is told from the perspective of a cop who arrests criminals and then has to testify against them, so....
Monstrous Regiment: Protagonist Polly's country, Borogravia, dubs the leader of the Ankh-Morpork forces "Vimes The Butcher". When she meets Vimes, he tells her that Borogravian propaganda is laughably amateurish.
There are various webpages on the Internet (such as this one) hosting a piece which claims that The Nutcracker was originally a dark and gruesome tale completely unfit for children. While it was dark and gruesome by some peoples' standards, many of the "facts" listed to support the claim - such as that Marie's family doesn't love her, that Marie is depicted as lying in a pool of her own blood after injuring herself, and that her parents lock her into her room to punish her - are completely untrue.
From Piers Anthony's Xanth series, we have the demonization of Magician Trent in the very first book, who lost the election to become King to the current ruler, the Storm King. As the loser of the political contest, Trent was demonized as an evil monster who transformed men into fish and let them suffocate on dry land (actually it turns out he turned them to fish in water, but they then unknowingly hopped up on dry land and then suffocated). Trent actually discusses the trope when Bink calls him on his perceived crimes; if the Storm King had lost the election, he would be portrayed as a doddering senile old fool who carelessly called up storms that went wild and killed people. All of this would normally be a huge spoiler, but in a rare triumph over this trope Trent becomes King Trent at the end of the book, and he's a major character in most of the books thereafter.
They Might Be Giants' "Youth Culture Killed My Dog" parodies this. "____ killed my dog" in general has become a common way to make fun of demonization.
The "villains" in all versions of Big Brother are often demonized.
This also happens in-game in Warhammer 40,000 as one of the Thoughts of the Day demonstrates:
A logical argument must be dismissed with absolute conviction.
And Lord Karamazov gives us this memorable line:
A plea of innocence in my court is guilty of wasting my time! Guilty!
The Imperial Guardsman's Uplifting Primer has several examples of this intended to prove mankind's superiority over all alien races. Unfortunately, the information given is so woefully inaccurate (Ork teeth can easily be pulled out, Tau can only see you if you move, Eldar tech is outdated, and other Obviously Evil traits that are the complete opposite of what they're facing..) one suspects it was written by a Chaos cultist.
Dungeons & Dragons was subjected to this in the 80's and early 90's from Christian groups (most notably Jack Chick and Patricia Pulling, the founder of Bothered About Dungeons & Dragons) believing the game encouraged witchcraft, satanism, suicide, and all sorts of other horrible things. It got to the point where TSR (the game's publisher at the time) removed demons, devils, and other monsters from the line (mostly by renaming them into tanar'ri and baatezu), stopped to call shamans "wicca" and funding studies to counter the claims.
In Psychonauts Raz's dad, Augustus Aquato is said to hate psychics, among other things, his image in Oleander and Raz's head, merged together, shows this quite a bit. "Man do I hate Psychics, and seeing my son happy!" The real version is, of course, nothing like that; in fact, he is horrified when he sees the mental image. "Rasputin, is that really how you think of me? Come on! I have WAY more hair than that!"
A well-popularized example: Back in the late nineties, there was some backlash against Pokémon by varying fundamentalist groups, who claimed that the games (and related series) promoted violence and occult imagery. Notably, the Vatican publicly defended Pokémon from these detractors. More specifically, the Vatican defended Pokémon on the issue of evolution, of all things.
Pokémon, among tons of other "new media", are still treated this way by many fundamentalists.
PETA's flash game takes this to a whole new level, especially as the organization has been sorta quiet for the last 15 years on the franchise.
Shin Megami Tensei I had this happen quite literally to several gods, turning them into demons; namely, Ahura Mazda (turned into Asura) and Ishtar (turned into Astaroth), by the Great Will.
Dragon Age II, the sequel to Dragon Age: Origins, both explores this trope as part of the plot and unfortunately uses the trope in a meta sense. The plot of Dragon Age II revolves around the conflict between the Templars and Mages in Kirkwall, and the defensibility, or lack thereof, of a system known as the Circle, in which mages (who in the game's setting can potentially be possessed by demons or use "blood magic" to control other people's minds and bodies) are taken away from their families as small children and made to live their whole lives in the Circle, with Templars to watch over them 24/7, ostensibly to teach them how to control their magic and themselves so they aren't a danger to themselves and other people. Unfortunately, because the nature of the system assumes taking away people's human rights due to what they might do, most people who grew up with American ideals will naturally side with the mages, because giving the Templars that much power over other men is going to lead to Templars demonizing mages. And that is in fact exactly what happens: mages are feared and hated, and Templars treat all mages as though they must eventually snap and turn into demons and slaughter everyone. So, to give the player a reason to root for the Templars, the Dragon Age II developers went far out of their way to make the Templars look justified. The mages' primary advocate, Anders, is portrayed as someone who demonizes the Templars and is irrational and unreasonable due to being possessed by the spirit of Justice. Almost every mage the player meets is an insane blood mage, the First Enchanter turns out to be aiding and abetting a serial killer because his use of magic would reflect badly on mages if revealed, the Templars are given an advocate in Fenris the elf that never learns his lesson or is ever proven wrong and shifts the "burden of proof" onto the innocent rather than the guilty, and the other sympathetic mage character, Merrill, accidentally makes a deal with a Pride Demon that results in the death of her Dalish clan's Keeper. So even as Dragon Age II tries to present both sides as having a point, since Dragon Age Origins players demonized the Templars while they were playing since the system is inherently open to abuse, the fact that the developers had to go this far out of their way to make the Templars have a point means that the mages were demonized, causing most players to side with the Templars since it looked like the Mages were all a bunch of lunatics and it looked like Anders had no good reason to complain or to object.
As if to balance this, the developers did see fit to include a few Templars who do abuse their power and authority: Sers Alric, Mettin, and ultimately Meredith.
It would be far more accurate to say that the game crafted a conflict based on both sides having extreme "bad apples" in them to show the player that what the detractors of each side fear so much is real albeit not nearly as ubiquitous as those who demonize the opposition claim. There are more than enough instances where the Templars show their oppressive, prejudiced behavior. The game runs mostly on Gray and Gray Morality where the only options are to pick your poison.
In-universe, the Mass Effect series is full of this. Humans are demonized as bullies who always use force to get their own way, asari are demonized as either whores or weaklings in combat or arrogant snobs who can only solve problems by talking about them, salarians are demonized as arrogant intellectuals and weaklings in combat and always solving problems by creating more and ruthless pragmatists with no concern for ethics or high ideals, turians are demonized as spiky monsters who constantly have sticks up their asses and always resolve problems by shooting them, quarians are demonized as beggars and thieves, krogan are demonized as mindless barbarians, hanar are demonized as weak pacifists who can't be taken seriously, vorcha are demonized as sewer rats who don't crap on the floor quite as often as varren, volus are demonized as greedy misers who can't do anything about problems but complain, elcor are demonized as boring, and the geth are demonized as omnicidal maniacs. And, depending on which sides the player takes during various conflicts, the player is free to join in on the demonization.
Vampire: The Masquerade – Bloodlines contains many examples of this, although it's played much more low-key than usual examples of this trope, since the demonizations aren't brought up too often. But when they are, the Camarilla are a bunch of tyrannical snobs and elitist pricks who simply want to enslave all vampires according to their whims! The Anarchs are a bunch of children who hate responsibility and would love an excuse to go on a rampage! The Nosferatu are a bunch of ugly monsters! The Toreadors are a bunch of superficial snobs who love only beauty and have no other values at all! The Malkavians are all a bunch of insane whackjobs! The Ventrue are all snobs who sneer down their noses at everyone else! The Tremeres are secretive and untrustworthy and probably wish to enslave everyone! The Brujah are all shiftless and thuggish and the Gangrel are all mindless animals!
Because he abolished slavery, Abraham Lincoln in BioShock Infinite has been demonized in Columbian propaganda (complete with horns) and John Wilkes Booth is depicted as a saint for assassinating him.
Lampshaded in Soul Reaver 2 by Raziel. Raziel encounters a stained glass mural depicting Janos Audron and describes Janos' history, ending with:
Raziel: I wondered, could Janos Audron truly have been as monstrous as depicted here, or was this merely artistic license by the Sarafan, who sought to lionize themselves by demonizing their darkest enemy?
The College Humor video "If The Other Party Wins" uses this (as a spoof, of course, since it's a humor website) against both the Democratic Party and the Republican Party of the United States during the 2008 elections, from the other Party's perspective:
If Obama wins (according to Republicans), Mexico will take back the Southwestern US states, New England will become New Canada, and weed will be grown everywhere. Also, American flags will be burned, students are rewarded for no achievements, terrorists and illegal immigrants will run rampant, medical care requires filling out a thousand forms, and the family unit will break down into pansexual group marriages between pot-smoking hippies.
If McCain wins (according to Democrats), the coastline will be submerged by global warming, Wall-Mart gets its own country, and the southern border is covered by an electric fence. Also, homosexuals are sent to jail, students are indoctrinated with patriotic jingoism, there is no money in the school budget to provide ink for test papers, students get drafted to fight in overseas wars, some students are pregnant, people are refused medical care because they're not covered, students fight each other with assault rifles in recess, the food is contaminated by oil spills, and people are monitored permanently.
Todd in the Shadows does this in a tongue-in-cheek way to Peter Cetera, claiming that he's a war criminal, that he caused the stock market crash, and that he killed Todd's dog.
Ben "Yahtzee" Croshaw relishes in doing this to the United States and Americans in general. If he so much as thinks Americans have anything to do with a game, he will spend a considerable amount of time demonizing them. This was aptly demonstrated in his Killzone 3 review, which included a lot of bile levied at Americans despite Killzone's creators being Dutch. Yahtzee attempted to dismiss people calling him on this by claiming that Americans were the game's target audience.
Captain Planet had Hitler's very gaze be as bad as pollution on Captain Planet. A big problem with the series was that the villains were into polluting for no good reason, which implied that anyone who polluted was just a plain villain instead of someone making a mistake—even a big one.
South Park often makes fun of far-left concepts, but sometimes goes too far by portraying some environmentalists as Axe Crazy. Not just eco-terrorists—all environmentalists. Or the episode "Canada On Strike", which implied people were starving to death during the 2008 Writers Strike. In fact, South Park is open to demonizing and attacking everyone. It was arguably its writers who popularized the demonization of Scientology example above.
In Drawn Together, virtually every character with conservative viewpoints are often portrayed as ignorant, racist, homophobic, overzealous religious nutjobs, or otherwise just plain heartless or hypocritical. Clara often exhibited such traits, especially in later episodes, and even antagonized some of the main characters due to her remarkably intolerant political and religious views. On the other hand, while other main characters certainly had unlikeable aspects to their personality, they're not nearly as close-minded (aside from the occasional joke about Xandir's sexuality) and Foxxy (one of the more liberal characters on the show) is often depicted as the voice of reason.
Similar to the above example is Family Guy. Conservatives, Christians, pro-lifers, and in general, people who don't agree with the writers' political views get this treatment, which unfortunately, affected the show's quality.
Exaggerated in the Simpsons episode "Sideshow Bob Roberts", which depicts the Springfield Republican Party as zealots who hold meetings (prefaced by a round of Ominous Latin Chanting) in an ominous castle straight out of a Hammer Horror film, and who at one point confuse a water cooler with their mayoral candidate.
Later they take a pot shot at the Democrats who are portrayed as a bunch of liberal stereotypes who are so ineffectual and poor that they have to hold their meetings in a random smoothie shop over lunch.
The Codename: Kids Next Door episode "Operation: B.U.L.L.I.E.S." depicts bullies as giant dinosaur-like creatures with names like Spitballosaurus and Wedgiesaurus Rex.
And in general, since the show operates from a Rule of Funny premise of "kids vs. adults", obviously "adults in general" are also demonized. They're either completely useless, or demonic monsters of some kind, or they're crazy whack-jobs, or they do things to make kids suffer for the sheer kicks of it.
Megatron in Transformers Prime does this for an amnesic Optimus/Orion, saying that Ratchet was the Big Bad and that the reason the Autobots call them "Decepticons" was as a form of Autobot propaganda.
Similar to the Teenage Robot example above, Horton Hears a Who! has the Sour Kangaroo tell everyone that Horton's sayings about the speck will lead to anarchy and gets everyone to cage him and destroy the speck. When Horton's words turn out to be true and the speck is saved, the Kangaroo gets shunned and hated.
Aku tries to attack Samurai Jack this way, by gathering children and telling them fairy tales where he's the hero and Jack is the bad guy. It doesn't work, but it made for some of the best moments on the show.