Have you ever done a ride along?
Yes.
Because this is the Internet and social media, a lot of nuance is getting lost, so this conversation isn't going to have a satisfactory resolution. But here's the problem as I see it:
Like all humans, police officers are more sane in fewer numbers. Get a group together, and they start to suffer from "group judgment" issues if there isn't a clear command structure. The same thing happens in any unstructured group - the tendency towards mob thinking increases the larger the gathering without an overseeing authority. So, hypergeneralizing, when you get a group of fifty line cops together with riot gear going into a situation where the threat is nebulous, you're going to get people who forget their training and/or self-restraint and they're going to do bad things. That's not an excuse, it's an explanation.
And yes, there ARE white nationalist pockets in police forces, just like there are in the military. And just like in the military, in some instances people with those views are the ones in charge. And yes, there are many cops (like military) who let the empowerment they feel by being licensed to carry firearms and employ force legally take them to a dark place.
So what we have is about a 75% to 80% population of cops who are what we would call "good" cops, thrown together in big groups with the other precentage, facing an undefined threat population of protesters who may be infiltrated by people with a vested interest in escalating and turning protests violent. The erosion of proper discipline in a group setting and a command dictum of force projection results in some officers going off the reservation in their crowd response, and in the moment many of the "good" cops either lose their heads or simply stand back and do nothing when their peers lose the picture.
Now, layer a martyr complex on top of this crap cake, and you have the situation we're in now.
I have a healthy respect for the military and the police because I have family members and friends in both. But I'm not going to absolve them totally of malfeasance when malfeasance is committed. If you're going to enjoy the pride of wearing a uniform and a lofty, egalitarian worldview of "the protector," then you also need to have the moral strength to acknowledge when those ideas are trampled by bad actors in the ranks and have the courage to turn that admission into redemptive action - even if it violates the code of "the brotherhood."