Pretty simple: do nothing and spend police resources on violent crime instead.
Once you have a good number of smoking-gun cases of repeat violent offenders due to DA inaction, then leak it to the media. Name and shame the DA, make sure the voters / people in power know where the weak link is and give them a better alternative.
Cops get apathetic because their arrests have no effect, but the paperwork can be useful to solve the fundamental problem.
Would you accept a world in which "1 in 1000" planes crashed because the pilot was on 3 hours of sleep?
There should be a media storm every time a police officer abuses someone, we should all collectively be outraged. A functioning society has to start with the front-line enforcers being responsible and trustworthy.
Being outraged at cases of abuse doesn’t mean you have to stop empathising with the difficult job that most cops have.
Reminds me of this quote: “almost everything in the world is broken and almost no one is evil.” Don’t let your anger at evil people make you reflexively think badly of their colleagues. Focus on your love of humanity rather than your hatred of authority.
There are about 1,000,000 police, so I guess 2 bad police events per month would be equivalent?