Only so many rules as to prevent this land of the free from becoming the land of chaos. Somewhere along the way we have to draw the line to save not only our own asses as a website but to save the people that visit it and contribute to it from coming to a hell hole.
I'm not adverse to porn or anything perverted. I think that if something might be offensive to somebody else, link to it with NSFW next to it (NSFW=Not suitable for work), so if somebody is on a public computer, they won't embarrass themselves.