I just see a couple sides to the "exploitation" argument, honestly. Yes, I think that some m/m writers are exploiting a trend. I think more are writing caringly about gay characters, though the authors' skill levels vary widely. But there are certainly a fair number of gay men who exploit the sexuality of their peers and/or themselves. Not that that justifies anyone doing it. I'm just saying that no community is completely pure here. Do I think that as m/m romance and erotica become better known, they'll stir up more controversy? Sure. I think the reaction will come more from fundamentalist religious groups as they realize that women are enjoying these books. Because it's "promoting a gay lifestyle." I just can't see much opposition coming from gay men in general.
There's an interesting dynamic at play here, as you get probably a large percentage of women readers who are closeted about their tastes in reading materials. That's got to give them some insight into what a lot of queer people go through. And whatever skill level the writer has, the subject matter itself brings up the question of gay rights. I'm sure some readers stay completely apolitical. But I think others move towards advocating more tolerance of sexual minorities. So many of these women readers seem to be married, with children. A certain percentage of those children will be gay -- I'm definitely one of those who believe that no matter what parents do or don't do, some kids will be gay -- and maybe reading books with decent gay characters will help those mothers accept their children for who they are.
Some writers are going to be more responsible than others, but I think those who write realistic, human heroes, people the reader can identify with, truly are good allies to the gay community.