War Is Hell. Anti-war works suffer badly from this. François Truffaut once said that "There is no such thing as an anti-war movie" because it will invariably look exciting up on screen. Another old saying is; "Soldiers love anti-war movies but never the way the maker wants", though these descriptions actually apply to war in other media as well as film. Plus, Truffaut's theorem isn't the only problem. Even if the work is intended to show how horrible war is it almost always backfires. While certain aspects of the war can be portrayed negatively, it's near impossible to make a work that is completely anti-war, regardless of what approach the creator takes, to the point where trying to make an anti-war work is nothing short of futile. There's a couple of reasons for this;
Even if #1 is avoided, and the work doesn't show any fighting and instead focuses on other negative aspects of war, such as the suffering of civilians or atrocities committed by one of the sides, it's a bit difficult to get the message across. Without showing the fighting, which is the actual war part of anti-war, the work can't actually show why the civilians are suffering or why the belligerents are committing these horrible crimes.
While the war itself is meant to be seen negatively, the works often go out of their way to portray at least one side fighting it in a positive light. In addition to seeing the troops fighting cool battles, the audience sees them committing selfless acts of bravery and maintaining strong willed attitudes of hope and perseverance. So the very fact that war sucks brings out the best in people.
A.) If only one side involved is like this, then it's only anti-war for that side. It's extremely pro-war for the other side because all it's done has justified them fighting, and the audience wants them to fight against the evil side.
The only time this doesn't happen are war survivor/refugee films, especially if the cast are survivors of a genocide and the enemy is an unstoppable tide of death and destruction and there is little to no talk of "fighting back" and instead is constantly on the run.
Another type of war film that generally averts this are nuclear holocaust movies like WarGames and The Day After (played seriously, that is; Dr. Strangelove is one of the most notorious cases to play this trope straight because it's a comedy). They often don't show battles and the whole futility of nuclear warfare elevates the conflict to an Enemy Mine between the mutually antagonistic powers to prevent The End of the World as We Know It. If the missiles do start flying, expect to see death, destruction, misery, and the horrifying end of humanity as people either get vaporized or slowly die of radiation poisoning.
Junk food is one of those things that it is hard to have An Aesop about because of how colorful and tasty it always looks. Any diet commercial will backfire horribly if they show the foods you shouldn't be eating (or should only be eating them in moderation) and say that you shouldn't be eating them (or only be eating them in moderation).
British TV chef Jamie Oliver tried to avert this by showing people their weekly intake of junk food all dumped together into a huge unappetizing mess. As Charlie Brooker pointed out, the resulting message was "don't eat your food that way".
This backfired again on Jamie Oliver as he tried to explain to children why chicken nuggets made from mechanically separated poultry are terrible and non-nutritious, as he carefully cut up a chicken and used the leftover carcass to make nuggets. The kids happily scarfed them down, to his sad amazement.
Dara O'Briain mocked this one as well, talking about Gillian McKeith's tendency to show people a table covered in all the crap they shoveled down their throats over the course of the week — and noted that the looks on their faces tended to be a mixture of pride and lust.
Any piece of anti-tobacco propaganda where the tobacco user actually looks pretty cool. Especially when it emphasizes someone trying to look cool by smoking or accuses the tobacco industry of glamorizing the use and then clearly identifies how they've played up tobacco usage to look cool, which the viewer may not have noticed before.
Drugs Are Bad. Anti-drug propaganda suffers heavily from this. Many works spend the first half detailing just how fabulous the wild and crazy world of drug-fueled parties are or throw in things like a funnystoner character or a Mushroom Samba. It's hard to take it seriously when they conclude with "Drugs are bad. You shouldn't do drugs."
Hilariously, there are multiple studies saying that anti-drug propaganda, both fictional works and real anti-drug programs, like DARE, not only fail to decrease the rate of drug and alcohol use among the participants, but in some places the rates actually increase. There are a couple of reasons as to why this is;
They expose kids to drugs at an earlier age. How many wouldn't even have known about these evil and destructive substances if they hadn't been told about them by the very propaganda trying to keep them off drugs?
It makes drug use seem far more prevalent than it actually is, making kids think it's normal, especially when they place emphasis on resisting peer pressure, which a lot of kids take as "everyone is doing drugs but you" and also "if you don't do them, prepare to be bullied and ostracised." In the twenty-first century, schools have been getting better about this, saying that everybody is not actually doing drugs and showing statistics to prove that it's not a really common thing.
When the kids get older and find out that some of the information given to them had been, at the very least, exaggerated in order to Scare 'Em Straight, (e.g. one joint of marijuana or one pill of ecstasy will kill you), they assume that all of it was and decide to try out drugs. For the kids to discover this, all it takes is them knowing one person who uses or has used drugs and didn't die or become a desperate junkie.
Even when being honest, describing the effects doesn't exactly make them unappealing. "Marijuana makes you feel happy and makes things funny. LSD and mushrooms makes you see bright colors and patterns. PCP turns you into Superman."
The Aggressive Drug Dealer doesn't exist, so if a kid does get approached by a drug dealer, they won't feel nearly as much pressure to buy from them and will realize that real drug dealers, even if they aren't nice, are much nicer than the ones on TV and may feel more inclined to buy from them.
Some anti-drug programs even tell students the current street value of drugs. Which, instead of resulting in "Oh, I would never do that, that's too expensive". sometimes results in "Hey, [local price] for [some drug] is a good deal."
Normal youth rebellion. Your parents and teachers don't want you to do this stuff, but they said that about all the good music, movies, and video games too.
Almost any video game that tries to remind us that violence is wrong. OK, here's your Godslayer Blade, Shootemup 6000, and a ridiculously complicated combat system that you must learn in order to see the story. Oh, and don't kill people, unlike the villain. Attempting to avert this often leads to the same problems as the anti-war film example above (if you don't make the combat in the game fun, people probably won't want to play it, etc.).
plastickiwi's submission: Wait... so you're telling me people download and burn their own DVDs... for free? Puck's submission: 90% of you didn't know you could download DVDs off the Internet until we fucking told you not to do it in ads before movies.
In addition, pirating your DVDs is a good way to be freed from those annoying anti-piracy trailers.
And work around the region codes in a No Export for You situation. At least when you do not have to worry about a language barrier.
Video game DRM can get even worse. Even getting beyond the Forbidden Fruit aspect (games with heavy anti-piracy measures, like several Ubisoft releases, tend to be heavily pirated - Ubisoft themselves once claimed 93% of their PC players were pirates - while GOG.com advertises a complete lack of DRM in purchases from them, and have become very successful rather than being pirated out of business), the most infamously-draconian systems, with several log-ins and security checks, also tend to be applied in a ridiculously-inept fashion: even at their most effective, since there are so many steps to it that can fail for a variety of reasons beyond the player's control, they punish legal players just as much as pirates (pirates don't have access to the log-in server and can't play, yay— whoops, server went down for maintenance/can't handle that many logins/hiccuped when they weren't looking/got pulled down a year later after the sequel was announced, so neither can legal players. also, the game detected software the developer doesn't like on your system, so now you're banned from every other game they have or will make), and at their least, they actively punish actual purchasers more than pirates (for all the same reasons as above, but not being actually integrated into the software in a way that the pirates can't just rip it out entirely and still have a working game). In extreme cases, people will actually purchase the game in question, then pirate it anyway just to actually be able to access what they legally bought.
The cameras step into the house of a teenage girl whose "life was ended" by pregnancy only to find that, somehow, her life goes on. It's harder to fear something with which you've become more familiar, especially when that familiarity proves the people trying to warn you away from something are exaggerating its consequences.
It doesn't help that most of the "struggling teen mothers" portrayed in many of these media are rich white girls who don't have to get jobs or miss out on school or social events to take care of their baby, and can often still get a guy (whether or not he's the father of their child) to go out with them. In a more meta sense, since these women have appeared on TV, they have a certain amount of fame they can leverage into speaking engagements, public appearances, and even endorsement deals, further making it seem more glamorous to outsiders.
There's almost inevitably — especially in documentary versions — a statement somewhere about how, at least in her own estimation, she's become twice the person she was and how it's really matured her, and how one just doesn't know what love is 'til one is a mother. Yeah, kids, don't do it!
Meta-wise, it's literally having the opposite effect on its audience; because of the increasing focus in recent decades on fame and recognition as being the most important value among teens and tweens, there have been instances of young teenagers who want to (or did) get pregnant because they think they will appear on television.
Anything against acquiring excessive material goods, whether it's discouraging greed or if it's anti-consumerism or anti-materialism, can easily fall into this. The story often has to show all the material things that people shouldn't be so greedy for, shouldn't waste their money on, or shouldn't define themselves by, and it's extremely difficult to portray these things without them looking cool. This goes double when the message is aimed at kids.
This happens a lot in Christmas works that try to reinforce the true meaning of the holiday; about family, about giving to the less fortunate, and how it's better to give than to receive, which is then undermined by showing all the awesome presents we shouldn't be so focused on getting. These also tend to end on Sweet and Sour Grapes, where the person is resigned to the fact that getting [awesome toy] isn't what makes a happy Christmas, only to receive it after all.
Hilariously, straight pro-consumerist works such as MTV Cribs and Pimp My Ride have had the exact opposite effect in retrospect, especially after the financial crash of 2008, since the extravagant bling and hoarding of resources are so unironically over-the-top that they are now seen as a huge part of what was wrong with 2000s popular culture. This was discussed by Charlie Brooker along with works like My Super Sweet Sixteen and the plethora of house hunting shows.
Charlie Brooker: For instance, here, her mum buys her a brand-new sixty-seven-thousand-dollar Lexus. But Audrey's unhappy, because she didn't want it 'til the day of the party. (insert scenes of Audrey complaining that her mother "ruined her life") Charlie Brooker: Actually, I think this might be an al Qaeda recruitment film.
For example, this ad warning about the dangers of anorexia shows a cadaverous-looking young woman◊ (Warning — NSFW image). However, while people without weight issues might be disgusted by sights like these (but it's not like they were going to suddenly become anorexic or obese anyway), they can also give grounds for denial: "I'm not anorexic/obese: I don't look like that!"
With weight loss in particular, the works can become icons as a goal to reach, or for viewers/readers blaming themselves. "Look at her, I couldn't even go as far as she did!"
In the case of some who have gone through the experience of having an eating disorder and managed to "beat" it, a lot of times they used pictures like these as "thinspiration" and seeing those images may trigger a relapse.
Going the other way, fat/body positive messages that are supposed to tell people who are seen as "large" by society's standards but are actually at a decent, healthy weight that there is nothing wrong with them could be used by actual obese people as an excuse to keep living an unhealthy lifestyle.
Sex Is Evil. Works that make arguments against sex or portraying it openly, whether it's discouraging sexual immorality and promoting abstinence or if it's arguing against the objectification of women.
The work inevitably has to show some sexual imagery, and it's pretty much impossible to show it in a non-appealing light, so either the sex or the portrayal of women comes off as appealing.
With works that promote abstinence, they often get screwed up by trying to balance out the message of how evil and dirty premarital sex is with how great and wonderful sex is once you're married. Unless the work resorts to outright lies, it really has no argument to show any differences between sex within marriage and sex outside of it other than the extremely murky area of "it's bad/sinful/immoral because I/our church/the Bible says so".
A.) It's no coincidence that the virginity pledge movement and abstinence trends like purity rings have coincided with rising rates of oral and anal sex among teenagers. While individual leaders and parishes have given their opinions on oral and anal sex, the churches of each sect have yet to take an official position on them. Because oral and anal sex can't result in pregnancy, this leads kids to believe they're just a little bit less sinful than vaginal pre-marital sex, and that it doesn't technically count because it's not the same as vaginal sex.
B.) Even with vaginal sex, kids can still find other loopholes, such as being engaged or being "spiritually married". They're not actually married, but they believe that you can still do it as long as you get married later. That part's pretty much in the Bible: ancient Israelite (precursor to Jewish) law specified vaginal intercourse between a man and woman who were both unmarried as being exactly equivalent to marriage vows, the couple becomes instantly married (modern equivalent being "common law" marriage). Hence what seems to be a punishment for premarital sex (marriage) is actually a logical consequence (and hence no ban on fiancee sex).
Fewer half measures. Sure, total abstinence is a more reliable way to avoid pregnancy and STDs than using a condom, but using protection is still way better than going unprotected. Programs that primarily preach abstinence tend to condemn protected and unprotected sex alike (and even those that acknowledge any difference between the two will often wildly exaggerate how often condoms or other forms of protection fail), so when the kids give in to their lust, they almost certainly won't already have a condom on them "just in case", may not know how to get and use one, and may be unaware of how effective it is and thus think it's not worth the trouble. Tellingly, areas that largely utilize abstinence-only sexual education tend to have higher rates of teen pregnancy than places that instead use comprehensive sex education.
Along the same lines, prostitution is devilishly difficult to portray in film without glamorizing it. Sex Sells, after all, and it's difficult to show a hooker plying her trade without showing what some of the appeal of that trade is. At the same time, if you do succeed in making prostitution look unappealing (via perhaps showing the cruelty and perversion of the customers or maybe the dangers of the trade), you're very likely to make your film rather unappealing as well, and then no one wants to watch it.
Any work of Speculative Fiction that preaches Humans Are the Real Monsters is inevitably going to receive a large amount of hate from people disputing the message and bringing up all the cases of people doing major good deeds to others with no compensation, because the audience is made up of humans, who naturally will disagree with the claim that they and their species are Always Chaotic Evil. It certainly doesn't help that the works in question tend to flanderize human behavior into the worst of the Jim Crow South or apartheid South Africa, and ignore that blatant prejudice is highly frowned upon in today's society. Oddly, the more general trope of Humans Are Bastards tends to get far less backlash, likely because it's rarely presented in the same all-or-nothing manner and at least some humans are presented as not, in fact, being bastards.
Any of the "technology is bad" messages and the tropes they relate to (whether it's a Green Aesop that suggests technology is at odds with nature, Science Is Bad, New Media Are Evil, New Technology is Evil, or the idea that "sometimes what's old is better than what's new and you shouldn't like or want some technology just because it's new"). They often portray the technology as something the viewers may well already have and get along fine with or at least know someone who does (video games, cell phones, etc), or as sci-fi stuff like flying cars, self-cleaning houses, etc, which just comes off as looking very awesome to the viewers (who wouldn't want a flying car?) Not to mention that it's not all that rare to be, or come across someone who is, simultaneously a Nature Lover and a techie.
If you're making a work for kids that with the message that Kids Shouldn't Watch Horror Films (or play violent video games, or read horror comics), you're almost guaranteed to have this problem. Not only do plenty of kids like horror movies and the like, but if the characters are shown enjoying one, children in the audience might end up sympathizing with them even if the Aesop is that they shouldn't indulge in such things.
Any work that aimed for "don't do X" and has a plot that goes something like "a character does X, and it's awesome until it backfires as a result of them doing something particularly stupid/reckless/selfish". For instance, "crime doesn't pay" may turn into "crime does pay; just don't make the stupid mistake that got the protagonist caught".