I can understand why this would happen. I don't agree with it, and it shouldn't have happened but if the interviewer is correct and he was moving towards them, perhaps with repeated pleas to stay back, then you can understand why one or two police officers may become edgy as he could have been concealing something.
Using this as an excuse to brandish all police as heavy handed is a bit unfair, I think by and large, from what I've seen on TV, most of these protests have been handled appropriately, and the violence is always instigated by the protesters. I have no sympathy for anyone who attacks a policeman.
The guy in question will probably lose his job anyway which is fair do's, and no need for the media storm surrounding it.
Pretty crappy interview though. Poor show BBC.