The real problem with police is that a large portion of them have an innate pathological mindset of dominance. That mindset causes delusions, aggressive behavior, and political actions to facilitate their delusions and aggression. 'Violence' is sometimes a side-effect of dominance-asserting aggression, and other times it is not, because there are a variety of dominance-assertion behaviors, but all of them are unjust and disruptive to society.
Therefore, police should be subjected to genetic testing, neurochemical testing, tone of voice analysis, and other psychological analysis, to determine if they have dominance-asserting temperament. The particular cops and prospective cops who do have that temperament must be summarily fired, blacklisted, and sterilized, and those who have perpetrated dominance-asserting aggression must be executed.