Sounds like someone doesn't know (or care) what can happen to protestors that are protesting the "wrong things"... Like oil and gas pipelines, for example, or training centers for heightened police militarization. Or foreign policy, even, that one has been happening for generations already.

Lol if only they would protest the right way, they wouldn't have to worry about anything, right?

Well the police can declare an unlawful assembly at any time for any reason, which tends to stir up even peaceful crowds. Not to mention being face to face with militarized thugs in riot gear, drones, helicopters, armored vehicles, mounted police, tear gas and "non-lethal" rounds. If I had a gas cannister lobbed at me, why wouldn't I toss it right back. Fuck em. ACAB.

You might have no intention of causing trouble, but still get rounded up. Happened almost every day in my city for several months during BLM protests. Mass arrests of people in the wrong place at the wrong time. The countless live streamed videos don't lie, each protest was non-violent until police agitated the crowd.

I don't go looking for trouble but I have my limits just like anyone else.

The police have absolutely ordered peaceful day time crowds to disperse while blocking every exit. They then decide force is necessary because nobody is leaving. Look up police kettling.