It looked like they knew exactly who they were going in to get and took the precaution of holding the others back. Notice how once the guy with the camera had calmed down he was allowed out?
I also intensely dislike the fact that the instant one of the officers merely held out his hands to stop the camera guy getting past, the guy instantly shouted 'assault, assault'. That's the kind of bias they knew they'd be up against and that's why they had so many officers there.
Also the 'journalist' who actually asked one of the officers about the man that had been hit. This may have been something off camera but from the footage we can't see anyone being struck, but obviously the news article would be 'police violently attack innocent protesters' - even though there was no assault (unless literally just touching someone is assault) and even though the officer himself said that he had not seen anything of the sort.