Nothing wrong with people peacefully protesting, whether they are right in their belief or not. There is a hell of a lot wrong with the looting and destruction that is going on alongside it. Yes, a lot of people who protest who want nothing to do with the looters, but there is also a subset of the protesters who are also part of those causing destruction. The murder should never have happened, and the officer who did it as well as those who just let it happen should be put away. So far this year there has been around twice as many "white" people shot to death by police in the US as those who are "black". But you don't hear about those. And yes, I know that compared to populace levels, even being only half is over representing, however you'd need to factor economic factors, different neighbourhoods and all that. The actual number isn't the point. Any deaths are too many. Yes, there are racist cops. There are also racist protesters amongst those protesting right now. But to say it's systemic is nothing but fear mongering, for either side. So many people are afraid and stressed and see enemies where there are none. The media, both social and mainstream holds a lot of responsibility in this regard. Much of the same criticism can and should be directed towards more right leaning media as well. But that's the media landscape you guys in the US seem to live in.
That said, again, everyone has the right to protest. Whether anyone agrees with them or not it's nobodies place to tell them they can't. But the place to protest is elsewhere, not in your manga.