On Agents Provocateur

Governments have found over the years that it works for them. They know they need legitimacy to stay in power over time, and movement violence gives them that legitimacy, what is often called "the moral high ground." They also need fear to stay in power, and movement violence increases the fear in the body politic. They work overtime to divide the movement, and movement violence is a great divider. And, perhaps most important, they desperately want to prevent new allies from joining the movement, and a frequent outcome of movement violence -- even property destruction -- is that potential allies stay away in droves.

(from http://www.trainingforchange.org/diversity_of_tactics)