The ACLU no doubt has reams of stuff on this.

I’ve read that the American Library Association protects books of all kinds. They surely have a website.

Tell them there is a book in the library that contains incest, homosexuality, witchcraft, murder, conspiracy and nudity.
Then give them a copy of the Holly Babble

I don't think there is any way to prove books are not harmful. It is not like trying to prove some substance is not harmful by consuming it and showing no ill effects. The books most likely will produce effects that the attackers think are harmful--thinking, empathy, knowledge...

What are the books?

We're having similar problems in Greenville, SC. I'm not as politically active currently but I think it's terrible how the right is trying to deny our existence.

Check with the Freedom from Religion website. I get a monthly newsletter from them as I support them, and there is a section in it that prints out articles about churches and church leaders who are arrested and convicted of sexually abusing children. More children are abused by so called christians and their churches than even I was aware of. Good luck.

Just look at the damage inflicted by the Buy Bull on children. Such mental defectives are a curse upon humanity.

What books are they protesting? Hopefully not Maplethorpe photography books.