Provocateurs always attach themselves to live mass movements and try to disrupt and discredit them through acts of individual violence or terror. They're the ones who say, "I know where we can get some guns", or "I know where we can get explosives", or, "this whole shit is going nowhere, we gotta do something and wake people up!" Of course, any experienced activists shun them, exclude them, expose them, etc., as a warning to others. But they prey on the inexperienced, those of good faith who feel a deep sense of injustice and frustration that the whole world isn't instantly joining the struggle.
The irony is, it doesn't matter whether the provocateurs are paid police agents, or just some wackos. The effect is the same - discrediting of the movement, implantation of a public perception that "they're just a bunch of terrorists", or "they're violent", or "they're dangerous", and always: "They don't understand our problems, our needs, our issues, they can never represent us."
That's why, for progressive people actually working for change (instead of bombing for change), it is essential to loudly condemn and expel such elements from any healthy movement - with vigour and contempt, and as publicly as possible.
Ah, but if they're not guilty - great. But I have a hard time listening to anyone who says simultaneously, "how do we know they're guilty", and then, "the RBC bombing is an acceptable tactic in getting our message out". They should make up their minds.
ETA: And yes, on this issue, Stockholm is right on the money.