Here's a quote from the wiki page of Armistead Maupin, which is very interesting:
"It's possible to write a novel now which has gay themes, which has any truth you want to speak, that can be sold to a mainstream publisher and sold in a mainstream bookstore, so the notion of people who've narrowed their focus to only write books for a gay audience for gay people about gay people is stifling to me; in some ways, it's another form of the closet, as far as I'm concerned. I think Jerry Falwell must be very happy with those little cubby-holes at the back of book stores that say 'gay and lesbian' - it's a warning sign, they can keep their kids away from that section. I'd like people to stumble on my works in the literature section of Barnes and Noble and have their lives changed because of it.
It's complicated. I don't want to feel any less queer, but I think for us to march along in a dutiful little herd called 'gay and lesbian literature' and have little seminars that we hold together is pointless at this point, it makes no sense to me at all. [...] I cringe when I get 'gay writer' each time. Why the modifier? I'm a writer. It's like calling Amy Tan a Chinese-American writer every time you mention her name, or Alice Walker a black writer. We're all discussing the human condition. Some of us have revolutionised writing by bringing in subject-matter that nobody's heard about before. But we don't want that to narrow the definition of who we are as an artist. [...] I don't mind being cross-shelved. I'm very proud of being in the gay and lesbian section, but I don't want to be told that I can't sit up in the front of the book store with the straight, white writers."
One of the best ways to end homophobia, IMVHO, is for people to have the realisation that gay people are normal everyday people and encountering gay characters in the media is one of the best ways of doing this. I think putting the stickers on the book might put off the casual reader and as mentioned earlier, sadly get some raised eyebrows and that's a real shame.
Also, there's then the possible interpretation that LBGT literature isn't for straight people, it's aimed at LGBT people so straight people shouldn't read it.