Actually, I've never met a gay person who wasn't far nicer than the average straight person anyway. People who face discrimination on many levels generally learn to be pretty careful about what they say and do.

Furthermore, your logic can be reversed. Straight people should be extra nice to gay people because after straights wreck their marriages or have kids they don't want to raise it's often the gays who adopt and love and raise those kids.

I think this is more lighthearted but I'm going to give a more serious answer. I don't think anyone has that kind of vested interest in the prolonging of any kind of label they happen to have involuntarily. I would put forth the idea that because gay people don't choose to be gay they have no reason to care how many gay people there are after they're dead.

gay couples can have a surrogate, and also we dont have to be nice to you if you arent nice to us