This is such a loaded issue.
My very best friend of 40 years happens to be a lesbian. She has a very good relationship with her present lover, and they have been together for years. She was married at one time and has 2 children, but couldn't live the lie. While we have discussed a lot of issues regarding homosexuality, the marriage issue has never come up, and I would tell her, as much as I love her as a dear friend, I would not condone marriage between them. I have no qualms with their right to sexual preference and happiness & co-habitation, but I do draw the line with marriage between same sex partners.
My only reason is that I believe marriage was meant to be between a man and a woman. Obviously, without the man/ woman union, (in whatever form), there would be no procreation. I do NOT believe God meant for men to be with men and women to be with women. But I will defend to the death a person's right to choose, as long as you leave marriage out of it.
I do believe same sex couples should have some sort of civil "partnership" rights in order to be able to have benefits and other rights, etc.
I just can't get over the marriage union tho. Sorry...it's ingrained in me that marriage is for men with women. The rest, I don't care about.