Based on discussions I've seen:

I think they would say(at least about women having sex with women) "It's not real sex, cause there's no penetration. That's why you use phallic objects as substitute penises." Nevermind that not remotely everyone does it like that. But they just don't take it seriously as sex.

For men it'll be the opposite because it's -gasp- anal sex(even though no one cares when it's between men and women) and can be discounted for that reason alone. Nevermind that men can have other types of sex, but then they get into the whole "not real sex" angle. So anal is real sex to them(otherwise they wouldn't be having conniption fits over it), but not the "right" sex. Except when between men and women, even though it's not reproductive like they say it needs to be. Yeah, the mental gymnastics..

Anyway, there are so many other inconsistencies I can bring up. You can't really win with them cause they have a very particular definition of sex, or more specifically, proper sex. Even if they almost never satisfy their own narrow definition of being reproductive with their own recreational sex(assuming they have any). So even if you use logic, they'd make exceptions of all kinds for their own orientation and behavior- just like that. And it's only okay when they do it.