This story is really hilarious, once you get past the utterly ballsy bigotry. Yeah, I could go on and on about the father's bigoted views of homosexuality, particularly those dirty lesbians, but I won't. That would be too predictable.
Instead, I'm going to laugh my ass off. It is so clear that these kids were looking for this book, or at least were goofing around the "naughty" section instead of doing what they were supposed to be doing. Which was looking for information on military schools. And what teenage boy isn't going to look at pictures of HOT LEZBIONIC SEXXX?
I'm a librarian. Granted, I'm an academic librarian, not a public librarian, but the gig works pretty much the same way. We have shelves of books which are catalogued and arranged in a way to make them easy for users to locate. Academic libraries usually use the Library of Congress Classification System, while public libraries use the Dewey Decimal System. So, there is very little chance that The Whole Lesbian Sex Book was shelved near the military education books. I'd say that this book would be shelved in the 600's, while the military books were shelved in the 500's. Close, but no, um, cigar.
Unless the book magically flew off the shelf and assaulted the boys into reading it, I don't buy it. And to think the father is just so outraged that his sons learned about a very real sexuality just tops it. I can guarantee that these boys knew what lesbians were, and probably what they did together, so Dad just seems to be grubbing for money and attention.