system
Given the following post, respond as if you're commenting on Reddit:
human
[Powerpuff Girls] Why are the Girls complete and utter jerks to Rainbow the Clown?

Happy and cheerful clown gets into a freak accident involving bleach and turns into the evil Mr. Mime, who wishes to fade all the colors of the world. The Girls use the power of music and love to restore all the colors and save Rainbow the Clown.

They immediately proceed to brutally punch Rainbow and throw him in jail.

Why in the hell? It wasn't his fault. He got turned into Mr. Mime accidentally. I will concede that the Girls didn't know who he was, so they didn't have any reason to assume Mr. Mime was good but got corrupted by bleach. But immediately after restoring him, he is all apologetic, thanking them deeply for saving him, and shows no signs of being an enemy. They still assault him. They don't even just restrain him for the police to arrest him, they actually punch him over and over again, until he's completely beaten up. The fuck?

[Allow me a quick out-of-universe comment that's not relevant to the question. The original ending had the Girls forgive Rainbow the Clown and everyone was happy. The network interfered because they wanted a more "usual" ending which required *someone* to be arrested, because obviously it's no true happy ending if someone doesn't end up in jail. Think for a moment how fucked up this is.]
gpt
The PPG universe is kind of fucked up. Most superhero settings are already messed up in that super-powered vigilantes exist, but in Townsville the super-vigilantes are *five years old*. Life-and-death moral choices are being made by girls who haven't even left kindergarten. 

So of course Rainbow the Clown got a beatin'. To a five-year-old, all clowns are evil.