There's two problems with the "I just think the state should get out of the marriage business" position.
First, it's either unworkable, or it's a semantic game. By that I mean that even most libertarians (unless they are complete anarchists) would recognize that there are some contexts in which the law should recognize a certain type of relationship that we generally call marriage: inheritance, child support, dividing property after a long-term relationship ends, power to make health care decisions for a patient incapable of doing so for him/herself, hospital visitation, etc. (Yes, in theory people could arrange many of these things themselves via wills, powers of attorney, prenuptial agreements. In practice they won't. And even if everyone was willing to plunge into all those negotiations and legalities, there is still enormous convenience in having a generally-understood "default" set of rules that apply when you're married.) If we're talking about the real world instead of Libertopia, there are also things like income tax returns and Social Security benefits where we'd want to give certain rights and duties to people who are married.
And yes, in theory you could use a different name for all of these legal distinctions, calling it all a "domestic partnership" or some such term, and reserving "marriage" for... well, what, exactly? Partnerships of which a religion approves? Well, presumably you don't think the State should be picking and choosing who gets to be a religion, so I would have just as much right to declare two people to be "married" as the Pope. So then your entire position boils down to an insistence that the statutes and legal decisions should use some term other than "marriage" even though that's what everyone is going to call it anyway. So what does that accomplish? It starts to look a lot like the gay marriage opponents, who attach great significance to having the state deny same-sex couples the term "marriage" because the opponents want the state to mirror their own prejudices.
Second, as a practical matter, the state isn't going to get out of the marriage business. So this position starts to look a lot like ducking the question. At a minimum, I think people who declare this position ought to come clean with their fallback position: given that the state is going to continue to have a legal status called "marriage," should it be limited to opposite-sex couples?
First, it's either unworkable, or it's a semantic game. By that I mean that even most libertarians (unless they are complete anarchists) would recognize that there are some contexts in which the law should recognize a certain type of relationship that we generally call marriage: inheritance, child support, dividing property after a long-term relationship ends, power to make health care decisions for a patient incapable of doing so for him/herself, hospital visitation, etc. (Yes, in theory people could arrange many of these things themselves via wills, powers of attorney, prenuptial agreements. In practice they won't. And even if everyone was willing to plunge into all those negotiations and legalities, there is still enormous convenience in having a generally-understood "default" set of rules that apply when you're married.) If we're talking about the real world instead of Libertopia, there are also things like income tax returns and Social Security benefits where we'd want to give certain rights and duties to people who are married.
And yes, in theory you could use a different name for all of these legal distinctions, calling it all a "domestic partnership" or some such term, and reserving "marriage" for... well, what, exactly? Partnerships of which a religion approves? Well, presumably you don't think the State should be picking and choosing who gets to be a religion, so I would have just as much right to declare two people to be "married" as the Pope. So then your entire position boils down to an insistence that the statutes and legal decisions should use some term other than "marriage" even though that's what everyone is going to call it anyway. So what does that accomplish? It starts to look a lot like the gay marriage opponents, who attach great significance to having the state deny same-sex couples the term "marriage" because the opponents want the state to mirror their own prejudices.
Second, as a practical matter, the state isn't going to get out of the marriage business. So this position starts to look a lot like ducking the question. At a minimum, I think people who declare this position ought to come clean with their fallback position: given that the state is going to continue to have a legal status called "marriage," should it be limited to opposite-sex couples?