I think zombie movies offer good simulations of how people will behave.

People tend to think about ethnic, religious, or racial divides, but there are also class divides. Gentrification only works because the police goes after the working class people fighting the developers and investors. Groups of people also have property rights.

A delusion can be good, though, if it can't be kept within sensible guardrails. Anarchy has learned from the past and quite vocally forsaken violence. Communism has only learned that they need more violence. Probably no ideal can ever be expressed perfectly in the real world.