I suspect that religion played a role in efforts to ban nearly all of these books. I do not mean to suggest that it was necessarily a primary motivator in all cases, but I'd guess that it was relevant more often than not. We've seen the same in most examples of limiting free expression.
I have read The Lord of the Rings
Again and again, we see someone appoint themselves as the judge of all that is decent and moral, assemble a following, and campaign to restrict the rights of others. Banning books is about many things - fear, ignorance, anti-intellectualism, superstition, etc. - but it centers on depriving others of freedom. Banning a book means that it is not available for others to read even if they wish to do so. It is about imposing one's preferences on others.
I suppose that this is part of why religion goes hand-in-hand with book banning: it helps to remove any of the natural hesitancy we might feel about imposing our values on others. If our values are divine, after all, we have permission to push them on others. Indeed, we may even convince ourselves that we are obligated to do so.
