As a former activist, I not surprisingly have a few thoughts...
A protest involves a bunch of people gathering and expressing their views verbally, waving signs, making speeches and generally being a pain in the neck. It can be a force for good, a force for chaos, a force for evil - or some combination thereof. But what a protest doesn't include is breaking people and things (that is what occasionally happens to protesters, not what they do).
A riot, on the other hand, is a bunch of folks that get busy about looting, arson, assault and the occasional homicide - and merits lethal response.
I suggest that in many instances the Ferguson and Ferguson inspired melee's have crossed that critical line - and that the appropriate response to looters and other violent felons involves utilizing all force necessary to bring their criminal activities to a screeching halt.
Free speech ends well before buildings are burning, witnesses are dying and the looting has begun.
I suggest that things have a fair chance of getting *far* more festive if police are not allowed to step in and end this - soon.