I was travelling a few years ago, and hanging out in the hotel bar in Portland, Maine, and I listened in on a heated conversation between some guy and a lady whose husband is a cop. They were discussing police brutality and the protests at the time (Baltimore maybe?), and the lady's point was basically "do whatever you want with regulating police behaviour, but I will take my husband coming home at the end of the night over anything else"
It's possible with the falling rates of crime, this may just solve itself (though increasing police training and standards is a good thing regardless).
Those Baltimore riots were sparked because a man who was in custody suffered injuries that could not have been caused any other way except by the police who held him, and all of them were acquitted. When people see that the system is intent on protecting the police, that means a lot of people aren't going to care whether that woman's husband makes it home or not.
Crime has been falling at the same time as police misconduct (not just the actual abuses, but the protection around them) has become more visible. Somebody needs to de-escalate it, and that would be a great place to start.