Depends on the nature of the crowd.
If it's a typical militant irresponsible OWS bunch of criminal losers, then yeah.
If YOU are the target, you can assume it's harmless silly string; your choice.
An LEO on the job? Not so readily. In a crowd that experience has shown there are mostly criminals, I give totally the benefit of the doubt to the cops.
The legality of assaulting someone publicly does not depend on the nature of the crowd.
The officer may have had legitimate cause to handcuff her.
He did not have legitimate cause to strike her.
Conservatives understand the difference, and won’t defend the latter.