The police "held back" at first when the violence started.

They didn't do anything until it got worse. They are partially to blame. I saw this first hand at the last march I attended where an alt-right group came a long distance to incite violence. The cops were there but just stood around in there perimeter and allowed it to happen until one of the guest speakers (an assembly person) called the chief of police.

It was at an Impeach Trump March in San Diego on July 2. There wasn't violence since the 2,000 resisters didn't fall for it. In LA however, there was violence. The cops today should've stepped in a lot earlier.

What is interesting is that historically the alt-right hates the government and the police.