It's absolutely possible that, if the police starts being violent, the violence spreads very quickly and cars get set on fire. Crowd control has a lot of strategy to it...
And his point seemed to be that police being "noticeably absent" from peaceful protests is more simply explained by the fact that those protests were peaceful rather than police presence being the source of violence.
Police brutality is a real issue but indiscriminately blaming the police every time they show up doesn't help the cause.
Let's not give the police the benefit of the doubt. Time and time again across the nation it has been shown that law enforcement is not for the populace-at-large but for the betterment of the state and its agenda - whoever the party in charge.