I just had a look at the American Library Association's Freedom to Read page and it would seem that the books in this display weren't actually banned but challenged. Librarians (and I am one) really like to conflate those two words it seems. Books are challenged all the time for all sort of ridiculous, frivolous, bonkers reasons. (Even, sometimes, for well articulated and thoughtful reasons.) But a challenge doesn't equal a ban. Many, many libraries and librarians (I'd hope all of them but I know that's not the case) will NOT ban books just because some crazy citizen thinks Anne Frank's diary was a downer.
I kind of wish more libraries/librarians were a bit more rigorous with the terminology. A display of books that have been challenged and are still available would be just as illuminating I think. As in, "Look, these books have upset some people but they're still available in your wonderful library because WE DON'T BAN BOOKS HERE."
That said, it's a great, eye-catching display.