Consenting adults should be able to assume the obligations of a civil union regardless of how their neighbors view their morality. As in other areas, adults should be able to follow the dictates of their own faith so long as they do not endanger or harm others, particularly minors.
Whether damnation awaits monogamists or polygamists or same-sex couples is a matter between citizens and their respective faiths. The government should address that aspect of marriage that concerns its insular needs: confirming the legal obligations of consenting adults. As for our politicians, there are levees to be rebuilt, corruption to end and wars to win.
Personally, the only thing that would interest me would be the legal contract anyway. Equal protection under the law. I don't give a tinker's damn about the religious stuff. I'd venture to guess that most homos feel the same way. Not that the distinction will matter much to the conservatives.