It's not just about the police shooting people (mostly unarmed black men). It's the unnecessary escalation tactics they use to create hostile situations. Talk to any black man, and they can give you an instance of a cop being overly hostile and trying to bait a civilian into a confrontation.. Here is an example of a guy going about his business and the cop doing everything she can to bait him..
https://youtu.be/Pb91NLHNa64