If anybody thinks this is a good idea, I'm looking forward to reading your opinions.
Let me be clear that I do not agree at all, in any way with this argument, I'm just answering your question as to what the opinion of people who like this think. There are books which contain explicit depictions of sex between teenagers. Why do you want teenagers thinking that having sex before you are 18 is normal? Kids shouldn't be reading stuff about sex (gay, straight, or otherwise) before they are adults. The on…
It's not actually primarily "books which contain explicit depictions of sex between teenagers" that are being challenged by this. It's books talking about the existence of gay, trans, and other queer people as something other than a horrible sin or a mental defect.
If it were just what you say, then yes, that would still be wrong, and stupid...but what it is, in fact, is wrong, stupid, and horrendously bigoted.