I want to be clear that the following is describing not advocating. But in some of the immigration marches in Seattle a few years ago, an anarchist with a black flag ran up in front of the march to "lead" it. He (you probably already guessed it was a he and not a she) was surrounded by burly men in union t-shirts and persuaded to drop back and join the march as a normal participant. I was too far back to hear the means of persuasion used, but he dropped back rather quickly.
Since my father passed away over a decade ago, I can describe another case. When he worked in a wire factory as a UE shop steward in the 50's , when the factory went on strike a particular sect of Trotskyites would show up at the picket line, and throw stones to provoke violence against the strikers, then run like hell to let the strikers take the consequences. This is nothing against Trostyites in general. Assholes come in all ideological stripes. The way this was dealt with was to beat the hell out of that sect when it showed up without waiting for stones to be thrown. If you want to call that policing you may, but it was the stone throwers who were doing the police's work for them.
Violence today against the Black Bloc would be very counterproductive and contrary to real points of unity among the protestors. But I think taking SA's idea and adding a bit of an edge, I think the chant should be "Police agent! Police agent". Even if they are not consciously agents it is true that they effectively they are police agents - doing a job the police pay infiltrators and informers to do on occasion. And no this is not civil discourse. It is a non-violent way of retaliating against an enemy, not against an ally gone wrong. Let them have the dilemma of either saying nothing and letting the charge stand, or denying that they are police agents and reinforcing the charge. It context of their actions that is more than fair.
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