I think if people like me, who do support the police in general, would be honest about it, we would have to admit that the job of police officer absolutely attracts a (hopefully small) number of the type of people who are into power tripping and abuse, and sadly as we have seen illustrated recently, racism. Worse case, a combination of all three as clearly is the case with Chauvin. I know for a fact that there are attempts made to weed them out before they even become cops. Obviously whatever approach is being taken to prevent those types from becoming cops needs some serious improvement.
Screws? Aren't those prison guards? What are you trying to admit, eyes shut!?!
All kidding aside, I would imagine prison guards are more prone to be abusive than bad cops. I don't know for sure, but I'll speculate that the pre-hire screening is not as thorough, nor would the standards for getting the job be as high. I'd like to be wrong about that.