One thing I will say is that Americans cherish their freedoms and they go to great lengths to express them. I've seen officers act professional in the face of verbal abuse and I respect that, they should have low blood pressure.
There are instances when I am sure the officer was going to go off but the camera in his face probably prevented them from doing so. There are some instances when the officer did go over the line, sometimes losing their jobs and I have to wonder "how many times and to what extend did they react violently to others who did NOT have a camera rolling"?