No reasonable person would suggest acting before all the facts are in. However, the great fear is that the officer might get a pass regardless of the facts. That happens often enough.
It amazes me how many people I have already heard making excuses for why this copper may have acted as he did--they aren't waiting for the facts, either. I mean, how @#$% obvious does the abuse have to be befor people see there might be a problem? Civilians never get this kind of consideration.