Technically (and sorry if anyone has made these scripture references), Leviticus 18:22 is the passage (which is part of Torah) in which God says, "[laying] with a male as with a woman, it is an abomination." In looking up the original Hebrew word used in the context (I don't have it on hand right now, but would be glad to get it if need be), the word "lay" essentially means "carnal intercourse," so we can safely assume God is talking about sex, ergo homosexuality.Then later in Matthew 5:17-19 Jesus reaffirms the Torah laws (which would include Leviticus 18:22), by saying, "For truly, I say to you, till the heaven and the earth pass away, one jot or one tittle shall by no means pass from the Torah till all be done." This means that until the heavens and Earth pass away, Torah (which includes Leviticus 18:22) is still active law.
This would really come down to a question of who you follow. If following Jesus means loving your neighbor and ignoring what God said, or if following God means seeing homosexuality as an abomination and ignoring what Jesus said, you've got quite a conundrum there, don't you? That is, assuming seeing it as an abomination means you have to hate them, and thereby, ignore what Jesus said.
As for my personal opinion, I am not a Christian, and personally don't care one way or another if gay marriage is legal. I'd say the 'sanctity' of marriage is pretty well screwed up anyway, what with a 50% +/- divorce rate, so big deal if gay marriage is legal. I'm just being adversarial wink