There was an inside joke in my old office that a resisting arrest charge (RA on the complaint) was simply a code word for "we beat the crap out of the defendant" It was a way to justify unprovoked assaults on citizens by the cops.
I am not so sure 'defunding the police' is so much a "bad idea" but it has been a bad slogan for sure. The meaning of the term for progressives is not to eliminate policing, but to make policing symbiotic with the community, so that police are a partner with a community rather than an 'Us vs Them' mentality. And the disparity of incarceration rates and people dying or being assaulted by police in this country vs others gives plenty of evidence for the system not being very effective or trustworthy. If you simplify it down to the most basic idealistic idea, putting all your money and effort into eliminating poverty, providing mental health support, providing rehabilitation etc is always gonna be better overall for society than ignoring all that and instead putting all your resources into arming the police and building more jails. And unfortunately, the public message of the current administration is just that: better arm the police, back them up in all circumstances, eliminate all safety nets and just let the poor and disabled fend for themselves. Boo to that.