I don't think this act itself is gay. I had a gf that would like me to cum on her tits or whatever, then lick it off and then feed it to her off my tongue. It turned her on.
But, its different to watch this sort of thing. I find nothing appealing about seeing a guy licking up his cum. But I can't get enough of watchin girls do it.
But how can doing something with a girl, and no other guy involved, be gay. I'll never get that. I'm sure not gay for giving myself a hand job!