The cameraman was 'assaulted' what does that mean? Someone shook a fist at him? Pointed a gun? The proper term would be 'struck' or 'battery' if he were hit.
'Police moved in on protesters after one of the marchers grabbed a TV camera, police said.'
Call it theft, call it assault. When a protestor engages an onlooker (or reporter or cameraman) in a physical manner, the police are rightfully expected to intervene.