Some riots and current outbreaks have certainly been caused by police.
In other incidents riot police have been filmed purposefully and willfully attacking already subdued members of the public; looking around first to check for observers of course! One of the cases the policeman put a weapon in the have of a subdued arrestee as a precursor to beating them.
These sorts of actions inflame the public and cause ongoing rioting.
It's been interesting witnessing quite measured, in relative terms, vigilante justice against some rioters too.
I haven't seen that footage, but of course I have heard of cases of violence against protesters. Doesn't really prove a deliberate approach to me. Maybe some police officers are also just human and get angry when people hurl stones at them and spit at them. If it's an excuse for the protesters, why not for the police. Sure, you'd hope they'd be trained in restraint, but at the end of the day, they are humans.
Also some footage may not tell the whole story. And maybe those cops were legitimately spooked by the umbrella. Better safe than sorry. I can't really blame them, wouldn't want to do their job.
In general, I think it would be wise not to provoke the police (or people with guns in general), don't wave around with objects that could be mistaken for guns, stuff like that? They should teach that in US schools, but every action movie teaches it, too. There is always that scene where a suspect reaches for their ID and then pauses because he realizes police might think he reaches for a weapon.
Yes, I've much sympathy with this. Police are human too - but just as if I get angry and lash out at someone in the street, without appropriate mitigations, I will be charged with assault - so too should police. That's rule of law in operation.
If you can stomach it then look on Reddit, the riot footage is illuminating IMO (of course remember the inherent selection and PoV biases).
But then charge the individual officers, not "the police".