I don't have the time or desire to read every post on every page of this thread, and I may be repeating some things others have said, but here are some facts:
1. Tons of animals are totally gay. It isn't exclusively human, and if being gay is defying the laws of nature, how come there isn't a species that practices heterosexual reproduction that has no homosexual population, excluding the ones not expansive enough to provide an actual sample size?
2. Wayyyyy over half of the world's AIDS cases are in sub-saharan Africa, so AIDS shouldn't be a factor in whether or not gay marriage is legal in the US. In addition, there are guessed to be 2.3m AIDS cases in North America and the EU, which combined have a population of just under a billion people. assuming 4% is a safe statistic, ~39 million people are gay out of the 974m, and even if 100% of AIDS cases were amongst gay folks, then not nearly all of them are gay. (edit: apparently Druiddroid was kidding on this one, praise whatever-the-fuck that nobody is that illogical)
Facts aside, whether or not two people can use different tax forms than single people shouldn't be a matter of religion. If separation of church and state were actually present in America (though it is meant to be, but that's for another time), then what some kooks wrote 2,000-4,000 years ago because they had voices in their heads and were seeing angels shouldn't permanently affect decent citizens today.
To touch on the opinion that homosexuality is gross, and the Bible is correct in condemning it, then why don't y'all have a problem with the story in the Bible where a dud's wife turns into a pillar of salt, and to console their father, the dude's two daughters had a threesome with their own dad?
The Bible isn't exactly a bad book; its stories are meant to teach its readers how to live in peace and not die of random shit. For example:
Don't have buttsex with dudes, because you might get a urinary tract infection.
All of your food has to be blessed by a Rabbi, not because he's magical, but because if you're eating lamb you found dead by a river and you're butchering it with dirty cleavers, you will fucking die.
Don't get tattoos, because the risk of infection isn't worth it. Barbicide or whatever the fuck you use to sterilize tattoo needles didn't exist during the writing of the Bible.
...and so forth.
Upon reading this post again, it's very shattered and rant-y, but I' tired and mad that people are making all Christians look like those people that hate vaccines and are obsessed with horoscopes and the people that think mediums who read a book on cold reading can commune with the dead.