Perhaps violence, like pornography, is some kind of an evolutionary standby system, a last-resort device for throwing a wild joker into the game? – J. G. Ballard

The limitation of riots, moral questions aside, is that they cannot win and their participants know it. Hence, rioting is not revolutionary but reactionary because it invites defeat. It involves an emotional catharsis, but it must be followed by a sense of futility. – Martin Luther King, Jr.