Look up Loving v. Virginia.
Yeah, I hate to say it but being from the South I can remember when I was growing up that there were still people bitter about that.
My point in bringing up the rule of government over the people mainly stems from licensing and various state laws. In my mind, the full faith and credit clause of the constitution should apply for every type of license, marriage licenses included. Having a patchwork nature of some licenses being valid everywhere (i.e., driver's licenses) and some that aren't makes for a very poor application of our own Constitution to the states.
That's what marriage boils down to, it's not a moral/ethical issue, it's a licensing/contractual issue. If marriage licenses need to be recognized everywhere (which they should be, again, under the Full Faith and Credit Clause), every type of license issued by individual states needs to be. Otherwise, the states should be allowed to regulate every type of license as they see fit.