Gullible Lemmings

"Look at these people; amazing how sheep'll turn up for the slaughter
No-one condemning, you're lined up like lemmings and led to the water
Why can't they see what I see? Why can't they hear the lies?

Maybe the fee's too pricey for them to realize..."

—Dr. Horrible, Dr. Horrible's Sing-Along Blog

Gullible Lemmings not only believe the villain but actively try to help him. They aren't Mooks or Les Collaborateurs, just regular citizens being what they think is a Heroic Bystander.

A subtrope of Dying Like Animals. Generally facilitate the existence of the Easily-Conquered World. See Horrible Judge of Character when this trope is applied to individuals. See also Good All Along and Burn the Witch.

Examples of Gullible Lemmings include:

Anime & Manga

In Death Note, there are interviews of the "man on the street" indicating widespread public support of the Knight Templar protagonists and their extreme "tough on crime attitude". This is in spite of the fact that in both cases the templars in question suggest that they plan on broadening their list of targets once they get rid of the truly evil people.
Saint Seiya: This was used as a humanizing move in the Hades arc. It's revealed that the Spectres in Hades' believe he is trying to bring about a Utopia Justifies the Means for all humanity... the "Great Eclipse" being the means. Of course, Hades just has a vague and nebulous all consuming contempt towards humanity and the living, and wants all existence to be in an orderly dead state.
One Piece:
- Nico Robin's tragic back-story had her betrayed left and right by the people who sheltered her so that they could collect the bounty on her head and hand her to the World Government.
- Speaking of Robin, her first encounter with the Tontatta dwarfs got off on the wrong foot. After accidentally discovering their village, the dwarfs (who are tiny little creatures who each have the strength of a giant) easily subdue her and tie her up, saying they cannot let her live because she has discovered where they live. They have a very good reason for such a policy, as dwarfs are worth 700,000 berries to slavers, and the tyrannical rulers of Dressrosa have already enslaved most of their species. Naturally Robin tells them that is not her intent, and is shocked when, by her word alone, they believe her. (Keep in mind, this is the first time they've met.) It seems dwarfs have a tradition that states if a prisoner is helpless but professes to be a good person, they must be telling the truth. Of course, Robin isn't lying, but one has to wonder if being so "credulous" (as she describes them) is how they wound up a slave race to begin with.
A Certain Magical Index: Stiyl and Kanzaki wipe their friend Index's memory yearly because the church told them she would die otherwise. The church was right, but only because they had put the curse on her themselves.
The rival Idol Unit Jupiter in the anime version of THE iDOLM@STER... at least until they found out their president's utter love for underhanded tactic, in which they've had enough and after too many times being ignored, they quit. In game, they decided to not use whatever tactics he promoted and fought fair and square.
- In the SP game, Hibiki is portrayed as this.

Comics

The citizens of Latveria are usually portrayed as genuinely fond of Doctor Doom, and willing to stand up for him against the likes of Captain America (comics) or the Fantastic Four. With good reason, he's responsible for freeing them from an unpopular dictator and subverting Reed Richards Is Useless by making Latveria one of the most prosperous countries in... Europe? All he asks for is the unconditional loyalty of his citizens. Some citizens are aware they will be killed horribly if they screw around, Depending on the Writer.
Following Marvel's Civil War, most of the US population is perfectly willing to acclaim psychotic murderers like Norman Osborn and Mac Gargan as heroes. Despite the fact Norman has been found guilty of being the Green Goblin, and consequently is a known lunatic and mass murderer. They proved equally willing to demonize well-known heroes like Captain America and Spiderman pretty much on command.

Films -- Animation

Madagascar: Melman the Giraffe is one, especially in the sequel.

Literature

1984: The Proles. They make up the majority of the working class people, and are seen as inferior to the Party, which views them like easily controlled animals. Seeing at how easily they are subdued by propaganda and the promise of the non-existant lottery aware, they might have a point. Nonetheless, their lives do seem happier than those in the Party, and the protagonist Wilson speculates that if rebellion is ever to happen, it will start with the Proles.
In the novel The Hunchback of Notre Dame: Quasimodo, our "hero," believes that Frollo's guards are the good guys and the gypsies are the bad guys. The actual situation is that Frollo's guards are trying to kill Esmeralda (the woman Quasi is trying to protect) while the gypsies are trying to save her. So you have Quasi systematically thwarting the efforts of the gypsies while making every attempt to help the guards.
Trollslayer has Gotrek and Felix encounter a village that helps an evil sorcerer who is holding their children hostage. The heroes don't find out that he's mutated them all into his personal army until after they've killed them all.
This seems to be the default mentality of wizards in the Harry Potter universe. People seem to believe anything published in the Daily Prophet, even if it flat out contradicts what was printed in an earlier issue without any real explanation for the change. This results in Harry being either idolized or vilified by the population, depending on the current unsubstantiated gossip. It also makes Voldemort's takeover of Britain in the final book a trivial exercise.

Tabletop Games

In Exalted, the Immaculate faith tends to turn most people Celestial PCs will encounter into potential Lemmings if their nature is discovered, as it preaches that they are "Anathema", demonic entities that seek to destroy Creation. The funny part is that the reputation isn't entirely undeserved.

Theater

Wicked: The citizens of Oz are like this, eating up everything the Wizard and Morrible say about Animals, and later about Elphaba. After trying to fight the propaganda and failing, Elphie turns this to her advantage when the rumor that "her soul is so unclean/pure water can melt her!" is put to the test.

Video Games

In The Legend of Zelda a Link To T He Past, a number of villagers believe Link to be a criminal who has kidnapped the Princess due to propaganda disseminated by Agahnim, who has deposed the king. Two will even call the guards to attack Link if she sees him.
In Pokémon Diamond and Pearl, the grunts from Team Galactic fit this description. They believe Galactic is a natural energy company, and only battle the protagonist because they were promised rare Pokemon in return. Little did they know they're evil leader's main ambition was to destroy this world and create a new universe he could rule. Brilliant, guys.
- The people of Unova are consciencious of their Pokemon to a fault. At Accumula Town, Ghetsis Harmonia makes a speech about the virtues of Pokemon liberation and how Pokemon can never truly be equal to humans while bound to a ball - and they just eat it up. It's only after Team Plasma gets a little too overt that the League starts taking action when all someone had to do to potentially derail the entire plot was present a historical overview of Pokemon crime history in the other four regions as a counterpoint back at Accumula. Oh, and for someone to give N some much-needed TLC; that'd be great, too.
Wizard101 most likely has few instances, however the most glaringly obvious example from the game is Crab Alley

Web Original

Dr. Horrible's Sing-Along Blog: Dr. Horrible believes this to be the case, and his plans for world domination are all wrapped up in plans to fix the world's problems and get rid of the flawed society which currently exists.
Used in The Spoony Experiment during his review of Final Fantasy VIII. Doctor Insano is elected President of the US, and his inaugural address consists of him berating the American populace for being so stupid that they elected a man who didn't even bother hiding the fact that he's a thoroughly evil Mad Scientist. This is of course a gigantic parody and lampshading of a plot twist in the game, where the Sorceress (who is Obviously Evil) is made leader of a nation and the people cheer for her even as she openly insults them.

"My election platform was to build a giant robot sawblade that would cut Canada off at the top and then attach it to Australia so they wouldn't bother us anymore! My vice president... is Fu Manchu! What the hell is wrong with you people?! I'm pretty sure that's not even legal! Oh, man, we are so going to jack this country up beyond repair!"

Western Animation

Avatar: The Last Airbender: The citizens of the Fire Nation are portrayed as pretty much exactly the same as the citizens of the Earth Kingdom, with the main difference that they're completely dedicated to The Empire after swallowing about a hundred years worth of propaganda and having information about various acts of war kept from them. While this could be attributed to any groups of citizens during the rule of a power others would call tyrannical, this really gets shown for what it is when the new Fire Lord, Zuko, takes power and instantly ends the war, at which point every Fire Nation citizen shown is completely behind him. Looks like they might just love their rulers too much.
- Of course, after the war, all we really got to see was a shot of twenty or so Fire Nation citizens rejoicing. For all we know there really could have been mass revolts, probably lead by high ranking generals who had a lot to lose. There's only so much you could fit in the episode's wrap up.
Superman: The Animated Series: Used to an expert degree in the series finale. Superman finally knocks over Darkseid, tells the citizens of Apokolips that they're free... and to his dismay, they help the fallen despot to his feet and take him off to recuperate. "I am many things, Kal-El... but here, I am God."
- This example borders on straight up Religion of Evil. The people of Apokolips are pretty much brainwashed slaves that worship their cruel and tyrnical God for being cruel and tyrannical.

Real Life

Many people will vote (in referendums or elections) against their best interest, for reasons of apathy, misinformation, or some combination of both.
- A particularly important subcategory of apathy and misinformation is Rational Ignorance. The effect of an election on a single voter, multiplied by the tiny probability of casting a deciding vote, may not be worth the many hours it takes to properly research candidates and referenda. People who cast fully informed votes (and people who vote at all, in countries where doing so is not mandatory) anyway must be quite altruistic, easily entertained by politics, meddlesome, and/or just plain irrational. We only hope that the first quality dominates...
  - Check election results the world over. It doesn't.