A monogamous gay couple cannot possibly acquire AIDS, nor any other STI for that matter. So much for "God's punishment".
Children are sometimes born with the virus also, and many acquired the infection via blood transfusions, so what sin is God punishing them for?
While it's true that in the West, gay men are still responsible for most of the HIV propagation, LGBT activism has helped educate the wider public and thus stop the disease from migrating into the heterosexual majority, so far. However that is not true in the wider world. Of 33.3 million AIDS cases worldwide, 15.9 million are female, and 2.6 million children, so it's very clear that your heterosexuality will NOT protect you from HIV infection; only monogamy and safe sex will do that.
African Americans account for only 14% of the US population, yet they account for over 40% of HIV/AIDS infections. It therefore makes no more sense to say that someone should not be gay in order to avoid infection, than it would to say that one should not be black, so as to avoid HIV/AIDS infection. A monogamous same sex couple is at no greater risk of spreading or catching STI's like AIDS than a heterosexual monogamous couple. HIV/AIDS is an almost completely avoidable infection. The key is safe sex practice, monogamy - every reason to encourage gays to marry. Lesbians are at zero risk of HIV/AIDS, yet they are homosexuals too.