How many times do you see perfectly friendly dogs not agree with each other. My view of this situation is you have two dogs which are usually well behaved (the pit was playing with kids right before and i know they are super people friendly dogs, can't speak for the white "fluffy cute" thing). What disturbs me is the viewpoints taken. That small dog could have been the instigator, which is usually the case, and the more dangerous dog, however, because of their size and color they are seen as cute and fluffy and innocent. Where as the pit has such a bad rap in a community that police and people are always on the defense.
As I am sure we all know, trying to hold a dog down forcefully is actually very stressful and causes a perfectly normal dog to lash out as well. I think this cop over-restrain the dog, placed more stress on the dog, which caused the dog to react to him. And yes, in a scuffle of dogs, hands are everywhere to pull the dogs apart, and its not the fault of the dog's that you put your hand in the middle of a scuffle. The cop is trying to cover is behind, yes it was dangerous because the dog "appeared" to go after him, but really the dog just didn't want to be held down. Its like saying a guy was pointing a gun at you, but in reality you gave him that gun and started to threaten him.
Dogs get into scuffles all the time, you pull them apart, check for scratches, and yeah, you might have to haul them away as they pull, but its in control. This cop stepped in post-scuffle, escalated the issue himself, and then took violent action cause he was too involved in the situation to just walk away 10 feet.