This one's always been funny but the blame for AIDS is more on promiscuity than homosexuals, at least in the modern day. If your partner is clean and neither of you have anyone else, you're never going to get an STD. That's not how they work. If you're sleeping with a hundred men a year, or a hundred women a year, or a hundred of BOTH, yeah, you're going to get an STD.
It is exclusively spread by gay men.
Gay men also are overwhelmingly promiscuous.