Before the internet we were passing video tapes/films, magazines, and prints around with porn and gore. Pre-teen me saw a lot of the kind of things you mention before the internet was a thing. The students at my school had pseudo-competitions for who could get the best porn/gore, earning kudos for the bloodiest gore or "hottest" porn. Often the lines would blur whens someone found scat or snuff but that's a different matter.

Later on in life, I think everyone knew "a guy" at work that had all kinds of taboo material. The Weird Eddies or Creepy Colins of the world had a black-market snatched from them when the internet got popular.