I have a friend that used to be super into watching morbid stuff like gore and snuff videos. He stopped a few years ago and last time I asked him he told me that he can't handle them anymore, same goes for another person I know.
In my case I've never been able to watch too much of those things, but I know I'm able to handle situations where blood and stuff is involved as I've studied anatomy with dead human bodies and also worked with injured people. I like to think I've had a bit of a healthier relationship with the effects of violence on humans.