I mean that entire trope is a gay person's proverbial wet dream, as to the vast majority of them the "unconvertables" are the hardest challenge and therefore have the most sex appeal.

Look at the most popular gay-catered media, and 99% of them have the main love interest as a guy who either isn't gay and doesn't want to be bothered with them and/or is anti-gay and while burning down one of their houses comes to the realization that he could send a "better message" by having sex with one of them. 50 shades of grey wasn't revolutionary, they just stole gay fanfiction and made it more marketable with straight characters.