Gay Liberation would move from more assimilationist demands like marriage to priorities Iike healthcare and employment, and you'd never see the "It's God's righteous plague on the evil homosexuals" backlash of the 80's. Africa would be in a much better state as well without the disease become epidemic there. Pop Culture would be completely, totally unrecognizable I do not even think you could start to estimate it.
Yeah. Gay marriage and monogamy were a response to the danger of disease. AIDS devastated the gay community, and the survivors had fundamentally different lifestyles.
Beyond gay folk, AIDS was the big killer for loose sex. In the old days, we had syphilis, the clap, crabs, and those sucked. Herpes was the new thing, and it sucked more, but it didn't kill. I remember when I was 18 (1992) my father gave me the closest thing to The Talk I was ever going to get from him:
"When I was your age, I was a virgin, but not for long. If I were your age today, I'd be scared to death."