some cops do genuinely join to help people and are not immoral people, at least not at the start. Arguably they are corrupted later on, though.

That's in line with the most police abolitionist position. The problem isnt that only psychopaths join, its just that some truly evil people arent prevented from joining and that the institution of policing motivates that other officers protect them. A cop that genuinely engages with the community, never arrests a non-violent offender, and deescelates all situations, if one exists is still a bastard if they cover for cops who don't.

Joining the cops doesn't make you a bad person, but not being kicked out for fighting corruption kinda does.