if anonymous is composed of human beings, it is subject to the sociological rules of any other movement in history. that's just reality.
Humans behave different in different situations. I thought any psychology major would know that.
Put a person in a crowd and they'll do what the crowd is doing. The police can attempt to remove the ringleaders, but the crowd has a mind of its own and therefore unpredictable. (Take the Fall of the Berlin wall which was almost spontaneous and had no central core leadership)
On the same note, put a man in a mask and a uniform and he'll be more likely to harm his fellow man with other men wearing the same thing.
Think of this situation as a rioting crowd of people wearing masks and uniforms. They are all there for different reasons. Some are protesting corruption, some are protesting economics, some are protesting religion, some are there just to loot, and some are there to vandalize.
Lets say a provocateur shouts at a man passing by, "that man burns puppies!", the mob puts asides whatever reasons they were there for and lynches the man.
The riot police come in and arrest the provocateur (or at least who they think it is), but the riot still is ensuing because most of the crowd is still doing their own thing, because the act of the lynching was not the original reason they were there..
I think that is what the OP is trying to say, this is just like how riots and lynchings work where things happen in a very unpredictable way.
After all most people who participate in riots and such events often aren't bad people, but rather get caught up in the moment.