Like most people, I used to think about criminals as those evil non-humans, and if you commit crime, you're a damned soul forever and you don't deserve forgiveness. It took an open mind and engagement to recognize how false that view was, and the rightousness that came with it took a while to get unused to. I don't expect that attitude to change. I'm not going to pretend I know what causes it, but I suspect it has something to do with vilification of criminals as a whole. Some of the worse offenders definitely deserve bad reputation, but most of them just make mistakes they come to regret later. If one starts to treat every mistake people around them make as a crime, the world becomes full of evil. We want to discourage our children from moral digressions, but I think the way we do this may actually encourage criminality. We dehumanize criminals in the same way we dehumanize enemy in war to make killing their soldiers much easier. We make them into outliers. For people who feel like they don't belong into mainstream society, the criminal layer may become more of a home to them, and there are few positive reinforcement loops to help them learn and grow. And when we grow up, we don't get to meet with a view opposing ours. Is it any wonder, then, that we keep thinking criminals are inhuman? I'm not saying that's all there is to it, but I think it affects the way we see criminals.
I feel you. I wish I had something insightful I could say, but unfortunately, I'm pretty much at a loss for words. I think I'll just say that the ideas of social stigmatization in general and "crime" in particular are huge and often difficult to grasp. Everything from economics to psychology to culture all bind up in a massive knot that's hard to unravel and it's something countless people devote their entire careers to working on. Sometimes we as societies take a few steps forward, sometimes we as societies take a few steps back, but I think overall as we learn more about ourselves our tools for tackling a lot of social problems become more sophisticated and we do a better job. Worldwide communication has helped a lot in that regard it seems. Partly because the exchange of ideas and information helps to create better policies and decisions and partly because our exposure to the world at large is showing us how human we all really are.