This essay, which I recommend more than the video, provides one of the best arguments for non-violent confrontations with authorities that I have seen. We have much to learn from our brothers and sisters in Spain, Greece, Egypt, etc.
The choice for nonviolence is not a choice to shun conflict, but rather to put this conflict in our own terms, choosing the scenarios and setting the pace.
...Violence makes us predictable: it reinforces the positions and roles (police repressor / protester victim). Calling a police officer a “hijo de puta” confirms the situation and the division of roles. Everyone knows who he is, what his identity is and what to feel towards the other. Surely this is not something very serious, but it isn’t really subversive either. Instead, the gestures that we have often seen at 15-M demonstrations compel the police positively, with forms of irony or empathic communication, to dislodge the situation: embarrassed, uncomfortable and restless, they interrupt the “automatisms”, challenge the clichés, ask questions, short-circuit the predictable, so that everyone knows he has to think, act and feel.