In the OT, anyway, G-d seems to be awfully quiet about female homosexuality...so perhaps lesbian marriage is fine? And if we're talking NT, G-d also seems to change His mind about various rules (keeping kosher being a good example)...does that make G-d a hypocrite?
You think about it, having gay marriage means that at least homosexuals (well, those who marry) wouldn't be having sex outside of marriage. You practically halve your sins that way! (I realize this is a dumb arguement. 'Tis a joke. Sort of.)
Now, there's only a few mentions about homosexuality throughout the Bible, but I do recall Jesus being pretty clear about his feelings on divorce (funny how not as many people are up in arms about allowing divorce in this country). Which makes you wonder...if we allowed gay marriage (which would, supposedly, be sinful), would gay divorce be really, REALLY bad?