Those flash bangs and other anti-crowd devices are accountable.
If they come out and say they don't know who threw one into the crowd, then you know its policy. If they choose to punish the guy, then you know he did it for kicks.
Like throwing a M-80 at a cat. Same mentality. Anyone who has used them or seen one go off know they aren't something to play around with.
When I was a kid my little brother would annoy me until I over-reacted and beat him up. Then he would run Mom & Dad and I would get in trouble. Everything I know a bout being an OWS protester I learned in kindergarten.