I think you are being far too pessimistic. In the US we went from sexual orientation being something that was socially acceptable to ridicule or attack with vi

I think you are being far too pessimistic. In the US we went from sexual orientation being something that was socially acceptable to ridicule or attack with violence, to widespread social acceptance and same sex marriage being law in most of the county in just 15 years - less than one than one generation. This change wasn't brought about by killing off every over the age 30. I think as long there is some kind of reconciliation method in place for people to say "I was wrong and now I've changed" without being attacked (like Sen Matt Kirk was), then social change can be facilitated much quicker than waiting for an entire generation to die.