Why do people want to ban books?

What books are these conservative hypocrites wanting to ban? And based on your title I assume that you are against the banning of books, am I correct?
If so, I commend you for supporting the First Amendment regardless of how strongly you may disagree with something.

Conservatives want to ban books that deal with race, gender and sexuality. And yes, IMHO the First Amendment (we have a similar one in The Netherlands) is for everyone so I think even racists have the right to be heard. Do you think some books or ideas sound be banned? If so: which and why?