I trust most of them, but there's some bad apples. I think they're over-tasked, and tasked to do things that would be better handled by a social worker or other specialist. Might be why there are so many problems. Because they can be targeted, and because they're armed, cops are trained to enter situations with more power, force, and tactical mindset than would normally be necessary, thereby escalating situations which can result in harm to someone who might only be having a bad day.
It's a job that I wouldn't want to do and I salute them for it (most of them), but I think there needs to be better standardized training and continuing ed for cops, and as a country I think we need to examine their role vs. the role of of specialists, as appropriate. When your only tool is a hammer, everything is a nail.