Many prison guards are inherently bad. If they had different character, they probably wouldn't do that job.
I'm not disputing that. That's not a good reason to eliminate prisons. The proper question seems to be - how do we collectively hire good/moral/fair/humane prison guards?
Irrelevant to the discussion. We're talking about how to morally deal with people who refuse to conform to the larger societies agreed upon rules. It's not as simple as *do nothing*.