system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are all mass murderers/serial killers considered mentally ill?

Is the label being overused? Is it not possible to be one without the other?
gpt
In order for someone to be a serial killer *and* not mentally ill, we have to accept a universe in which killing a bunch of innocent people is logical, expected, and reasonable.

I don't think you'll find very many civilized people who will say that killing a string of innocent strangers is ever a reasonable or logical thing to do. The only conclusion one can draw then is that such a person has something wrong with them in the head.

I would reverse the question to you: Can you describe a person who is a serial killer, but that you would not consider mentally ill?