[NSFW] Do you think it's wrong to have sexually explicit books opened freely in a book store?

I went to Half Price Books today, and I saw an opened Kama Sutra Manual book in the History section, complete with real life examples of sexual positions. The book store sells used books, so I’m assuming the book never had plastic wrapped around it. I’ve also seen picture books at Barnes and Noble with graphic nudity. I think it’s funny how movie theaters are so strict about movie ratings, but book stores have no policy about books and nudity. What do you think?

By the way, I’m in no way a prude, I just think it’s interesting.