I am a Christian. I was baptized in the Baptist faith when I was seven, and though I am denominationally-promiscuous, I have remained a fairly devout follower of the Bible throughout my adult life. I believe that the Bible represents the word of God, and is a guidebook for navigating through this broken world.
So comes now the issue of gay marriage. Leviticus 18:22 states "Thou shalt not lie with mankind, as with womankind: it is abomination." I don't think there is too much wiggle room on this one...homosexuality is considered sinful in the Bible, and I have no reason to deny such a claim. However, I find myself in a bit of a quandary as a libertarian, because the ability to be free to choose is the central pillar of the system. Would it be right for me to declare something fit for ordinance simply because it offends my personal belief system?
In a word, no. I believe that gay people should have the right to be legally joined. There is no legal foundation to deny them such an ability, and any argument to the contrary will always invoke the notion of a shared societal belief system. I don't know if I agree that we do have such a thing, but I think that it's irrelevant regardless because people remain free to shun or verbally disagree with homosexual unions. Furthermore, I am completely against churches or clergy being compelled to marry gay people if such a union violates the tenets of their faith (as it does mine).
I have heard many people declare the United States to be a Christian country. Whether or not I agree, it is certain that the United States is decidedly not a theocracy. Secular rights should extend to all people, and laws that preclude people from behaving in a compassionate manner (say, a gay person is dying in a hospital, but their partner is forbidden to see them) simply don't make any sense. I don't agree with homosexuality or gay marriage, but I support the rights of adults to choose.