One more point: the comparison between homosexuality and theft, adultery, or other issurim that people have pointed out is seriously flawed.
We didn’t need the Torah to tell us that it’s wrong to steal or to cheat on your spouse. We DID need the Torah to tell us that we shouldn’t marry same-sex partners. If I weren’t frum, I would 100% support gay marriage, because why not? Whom is it hurting, right?
So, while it’s still assur to marry a same-sex partner or to engage in homosexual activity, we should have a lot more compassion and understanding for those who do so, AND for their straight “allies”.