[Re: What is violence and non-violence, and who gets to define them in the context of social movements?]
Myself, as a participant in the anti-globalization movement, when I hear this question, I think of the FTAA protests in Quebec in 2001, when the police filled the entire city center with so much tear gas it even entered the ventilation system of the building where the heads of state were meeting. The only reason we could breathe at all—the only reason we weren’t cleared out like so many of the occupations last fall—was that courageous people in black were throwing back the tear gas canisters. They were the only thing protecting us from hospitalization or worse.
The next day, one newspaper article read “Violence erupted when protesters began hurling tear gas canisters at the police.” In practice, “violence” is code for illegitimate use of force: anything that interrupts or escapes the control of the authorities.
That explains why slumlords forcing rent increases on tenants isn’t violence, but defending yourself when the sheriff comes to evict you is. Pouring carcinogens into a river isn’t violence, but disabling the factory that produces them is. Imprisoning people isn’t violence, but rescuing people from officers who are trying to arrest them is.