@carla: ok, my bad. It is good that you agree people should be able to access some books at the public library that you would not allow in your personal library.
What if one of your (perhaps hypothectical teenage) children came home from the library with a copy of 'Mein Kampf' having heard about it in history class. Would you allow him/her to read it? Would you want to discuss what they thought about it?
What if they wanted to read the Koran? Would you allow it? What if they wanted to read the 'bible'?