I specified that I wasn't comparing the two. I'm comparing the formal structure of the situations. In both, the inequality is hidden poorly by the language of equal rights. Also, if you are a true libertarian, you shouldn't see any distinction between sexual orientation and ethnicity with regard to rights. That is an established, true libertarian position.
Also, when you say you're for leaving it up to the states, do you mean just gay marriage, or marriage in general? Should heterosexual marriage also be left up to the states, so that some states can ban/not recognize them?