re: Ferguson/Brown Protesters block Atlanta freeway during rush hour

I think something needs to be clarified.

If a unlawful protest breaks out what is the main goal for the police.

to prosecute as many people as possible?

work to get the situation in control to limit property damage, injury and possibly death. Also if involved to keep traffic flowing as it should?

I think the later is more important than the former, meaning if arrests makes it more difficult to get the situation in control than it may be better to let them protest but control them to allow traffic to move like normal.