They'll eat each other

"To them you're just a freak, like me. They need you right now, but when they don't, they'll cast you out. Like a leper. See, their morals, their "code"... it's a bad joke, dropped at the first sign of trouble. They're only as good as the world allows them to be. I'll show you. When the chips are down, these uh, these "civilized people", they'll eat each other."  - The Joker from The Dark Knight
 

Thanks, Becky!