Stalin re-criminalized homosexuality, but Lenin abolished the old laws against it. I'd say both of them would at the very least acknowledge that the modern state of things is indeed a progression away from the atomic family unit that capitalism created. The only hangups they might have would be on individualism, but that doesn't really apply to the LGBTQ community specifically and in fact that community has some of the strongest and most active solidarity of anything right now.
After seeing the current state of things, they'd have no choice but to support the movement as an integral part of any proletarian revolution. Especially when 99.999% of the gay community is proletarian. Even in my smaller southern town, about half my co-workers are gay or bi, and about half the service workers here are too.