I feel very similarly towards Critical Mass as I do towards Burning Man:

The ideals behind it are fantastic, but have been co-opted by radicals as an excuse to behave poorly and without concern for the ethic behind the original movement.

I think that might also apply towards the police, at least in this situation. I'm sorry that it happened, and that the Man was so oppressive to some poor hippy, and that some poor hippy's freedom of action was taken away by some jerk with a badge. I don't ride Mass, and I don't interfere with the flow of traffic, so I'm not worried about "what people will think of me because of this". Instead I'd rather act as a calm and right example of how cyclists and traffic can co-exist.