Uttering death threats is a crime in most nations. So they would hopefully be put in jail long before they acted upon those thoughts. If someone is that disturbed then there's something wrong with them on a fundamental level -- be that nature or nurture. What I would hope for that person is that they're locked away from society, but treated as well as they can be considering some safety measures need to be in place for even prison guards to interact with someone like that.

I'm not arguing at all that we never lock anyone up, that's absurd and anyone who thinks that is probably intentionally misunderstanding my meaning. I just think that treating people with as much dignity and respect as we can is the right thing to do in all circumstances. Dehumanizing and othering people is what fascists do, if we want to call ourselves the good guys, we can't act like fascists. It's just plain wrong, and it's evil.