Frankly I am a bit cynical about politicians declaring the need for police reform. In my country protests are regularly "subdued" with excessive violence but the decision to handle it this way comes from the top, not from police officers.
I think clearer legal rules would help. Also maybe teaching people how to behave in case law enforcement conducts a search. The ability for surveillance and raiding homes should certainly be under intense scrutiny. Because I think the fear of decision makers is the main driver we might see some problems.
> I've been in a few protests and I can easily say that I have never seen more hatred in someone's eyes other than the cops that were beating up people.
That can be true for protesters and criminals too. I am aware of the irony of mentioning them in the same sentence. But the "psychology" study should show, that police is just often required to just do the dirty work and some might adjust to the crime they see in their daily routines. The systematic problems are programs like war on drugs or excessive militarization.