You Rebel Scum

A villain of the series who is nominally an authority figure (especially one known for self-righteous priggishness), or a minion of said authority figure, captures the heroes, usually in some criminal (or at least 'anti-social') act, can't let it go without declaring 'You filth!' or some similar self-righteous epithet. Used to underscore the opinion of the law and most ordinary citizens that the heroes are Exclusively Evil even though the audience knows that they are really heroes.

A similar sort of remark is almost always made by an underling if the Big Bad has to make a deal with some underhanded or socially outcast allies; for example, the line 'Bounty hunters. We don't need that scum!' in The Empire Strikes Back. If one of the heroes of the series says something like this under those circumstances, it's usually a setup for an An Aesop about tolerance.

Examples of You Rebel Scum include:

Anime and Manga

The Titans in Zeta Gundam are fond of this.
The dub Yu-Gi-Oh! GX has Slifer Red students being frequently referred to as "Slifer slime" and "Slifer scum". (In the original, they were mostly referred to as "dropout boys").
- Yu-Gi-Oh! 5Ds has Ushio/Trudge, who calls Satellite residents (especially Yusei) "trash" on every occasion. He stops after his Heel Face Turn.
One Piece: CP9, especially Spandam refers to the Straw Hats as "pirate scum" when they dared to infiltrate Enies Lobby and stand against them and the World Government. Spandam even calls them "tako-pirates" (octopus-pirates) for good measure.
The "11s" from Code Geass.
The Empire in Legend of Galactic Heroes refers to the Free Planets Alliance as "Rebels", despite the fact that no FPA planet was ever part of Imperial territory.
Some of Fate Averruncus' minions in Mahou Sensei Negima, especially Homura and to a lesser extent Shirabe.

Comic Books

In early Marvel Star Wars, the Imperials call Rebels "slime-lickers" quite often. Soon enough the Rebels start using that epithet too, though.

Film

The eponymous case in Return of the Jedi. And just because this trope can fit into each movie of the original trilogy, there was Leia being denounced as "part of the Rebel Alliance and a traitor" in A New Hope.
The Agents (especially Smith) in The Matrix trilogy derisively refer to the resistance fighters as "only human."
In Hotel Rwanda, the Hutu militants refer to their enemies as "Tutsi cockroaches".

Literature

The orcs in The Lord of the Rings seem to use 'scum' as their preferred insult. 'Maggot' crops up once or twice as well, but only when referring to other orcs who are their direct inferiors.
The Animorphs' enemies, the Yeerks, refer to them as "Andalite bandits," "Andalite filth," and "Andalite scum," in that order of frequency. Not knowing the Animorphs' own name for their team, the Yeerks have made "bandits" the standard word they always use to refer to said team.
- On the flipside, Andalites (including Ax) are awfully fond of using "Yeerk filth" themselves.
The security guard in The Hitchhiker's Guide to the Galaxy. "You scum! You vermin! What do you want to drink?"

Live-Action TV

Parodied in the Doctor Who story "The Horns of Nimon", with a guard who addresses his prisoners as "weakling scum" every single time he speaks to them.
Whenever the main characters are captured in Stargate SG-1, a Jaffa or Goa'uld will usually say something like this. Usually involving something like "You dare stand up against your Gods?". The most common response, especially when Jack O'Neill is present, is something to the effect of: "Well, duh!"
- A more straight example of this trope: every Goa'uld or enemy Jaffa will call Teal'c a "shol'va" (which is Goa'uld for "traitor"). Every one. Without exception.
  - Not that he really objects, and as the Jaffa resistance grows he's still called that, though not in quite the same way...
In Buffy the Vampire Slayer‍'‍s fourth season, there is a military group called the Initiative. After Buffy and her friends run afoul of them, the military commander refers to them as "anarchists"—a label Riley takes up when he decides his love of Buffy, friendship with the others, and the things he's seen cannot be ignored in favor of his military career.
The League of Gentlemen: "Dole scum".
In the Firefly episode "Bushwhacked", this is the reaction the commander of the Alliance ship has toward Mal and his crew once they arrest them. Aside from the fact that Mal was on the Independents' side of the war, they found a second-generation Reaver on the ship, thinking he was a tortured prisoner, and the commander assumed that because Mal was an Independent, he was a psychotic terrorist, too.
- In another episode, a belligerent drunk starts insulting Mal for wearing a brown coat and therefore being an Independent sympathizer. Mal's response is to deck him across the face.

Video Games

The same line was used once in StarCraft. Somewhat of a subversion, as the person saying it is an unarmed civilian scientist who immediately gets killed along with his colleagues by said rebel scum.
Various enemy soldiers in Crusader spit out things like "Rebel scum!" immediately before opening fire.
In The Elder Scrolls III: Morrowind, the guards in the city of Vivec (Which according to in-game dialog did not allow "outlanders" into the main city until recently) are commonly heard to say things like "We're watching you, scum." and "Move along scum." to the player. They become nicer to the player if he joins and advances in the Tribunal Temple (who they serve), but become would be lynchers if the player is acknowledged as The Messiah, but hir claim is not backed up by one of their gods
- Oblivion: STOP RIGHT THERE, CRIMINAL SCUM!
When provinces revolt in Victoria: An Empire Under The Sun, the resultant fighting forces are referred to in-game as "rebel scum."
"Rebel curs!" Or "Rebel scum!" is a common exclamation by Palamecian soldiers in Final Fantasy II.
In all games of the Europa Universalis series, rebels could pop up in provinces for various reasons, and until an expansion of the third game differentiated them, they were automatically at war with all countries and actually referred to as "rebel scum".
Mooks in Red Faction will occasionally yell this at Parker as they open fire on him.
In the MMO Dofus, the militia members of the warring cities of Brakmar and Bonta will refer to you along these lines if you speak to them whilst showing the opposite alignment's wings (works like badges, only more feathery).
"Filthy Alliance!/Filthy Horde!" is a stock phrase among the players in World of Warcraft.
The random lines spouted by troops in Star Wars Battlefront II include "you Rebel scum!" for Imperial officers and "Rebel scum this!" for various Rebel troops.
- "Rebel scum" turns up in a lot of Star Wars games. "Stop, rebel scum!" was one of the stormtrooper dialog choices for when one first noticed the player in Dark Forces.
The Final Boss of Project Wingman calls you and yours dogs for most of his earlier appearances, but it culminates in his spending all of Mission 21 ranting about how none of this needed to have happened if the damn ingrate rebels you're fighting for hadn't tried seceding.

Real Life

Partial example: In the party-game "Mafia" (or "Werewolf"), the majority party (whose goal it is to figure out who the Mafia/Wolves are before they are killed) is called "Town" and the minority party (whose goal it is to kill the majority party without being discovered) is generally referred to with the blanket term "Scum".
- Especially in the more complex games with more than two factions: There, the "mafia" refers to the one specific faction, and "scum" refers to anyone whose win condition is incompatible with the Town's (or, anyone who town has to kill to win). (So mafia members are both mafia and scum, a cultist or Serial Killer is scum but not mafia, and survivors are not town-aligned, but are not scum since they can win with the town.)
Muammar Gaddafi and his sons were fond of this, frequently referring to NTC partisans as "rats" and "dogs".
Insults like this are a staple of authoritarian regimes, eg. the Nazis' "Jewish Bolshevists", Soviet Russia's "bourgeois scum", Maoist China's "capitalist roaders" (both meant to mean to accuse the subject of their ire of being Corrupt Corporate Executives) and so on.