Governments ban books for any number of reasons: sexual content, religious blasphemy, racism, and violence, to name a few. There are such things as books that some people should not read (the anti-Semitic forgery The Protocols of the Elders of Zion comes to mind). But the act of banning a book is always a terrible idea. It not only crushes free speech, but it elevates the book and it’s author to martyr status, which often is the exact opposite of what the banner wanted.