Censorship in the library begins with the refusal to shelve donated conservative books in the first place. It continues with the purging of old books that are not damaged or "outdated" by more current information (check your library booksale carts and tables).
Unfortunately that does happen. I like libraries. There should be enough room for books that others deem offensive or offputting, regardless of what the content is. That’s why there are so many decimels in Dewy’s system.