I think of porn the way I think of movies or TV: there are all sorts of different stories, genres, settings and messages. Just because there are a lot of movies and TV shows that are sexist and degrading doesn't mean that we should BAN all movies and TV entirely, and never have any entertainment or fantasy.
Have you seen feminist porn? Amateur porn? I'm a woman who watches porn, and I NEVER watch any of that mainstream cheesy scripted crap that everyone else talks about. It disgusts me more than it could ever arouse me. Porn is a vast medium just like non-porn movies.
Can porn be abused? Yes, absolutely, but like Trippin said, so can alcohol.
Do cave paintings and erotic sculptures also destroy relationships and your brain? I think not.