Banned Books

I just read the list of banned books. Most of them I either read on my own or in school, and I found nothing whatsoever wrong with them when I read them. So why were they banned?! I mean, my teachers in high school, elementary school, college told me to read them, and they seem pretty great. Nothing to censor about them, so why censor them now, is my question. It's puzzling to have them censor cause some of the books were all the century's 100 most popular list or whatever it was back before the new millenium began. So what the reason for the censorship?
I mean, a lot, whole a lot of kids watch violent movies and play violent video games. Not only that they tween and also teens watch sexual action on TV, so they're probably desensitized by it by now. And they either read or watch Harry Potter, Lord of the Rings, Twilight, and every other vampire rip-off there is so there is no reason to censor some books that they don't really for. Other than the fact that the schools make them read it. If the censor those books, they have to read the popular teens/tweens books filled with gore and other gruesome stuff. Those are stuff that should be censored.