Well, when SCOTUS does finally take a case where they are asked to rule on the fundamental question of marriage equality for same-sex couples, I am sure that there will be countless amicus briefs supporting your belief filed by some of the states and the usual groups. And those briefs will be weighed against the reality of legally married same-sex couples from those states that allow it and those couples being recognized as married by the federal government. Lets see... how will the court rule.Rather simple actually, the state has a compelling interest in the relationship itself, the male female union. All men, and all women, regardless of self professed same sex attraction are still men and women, and thus they can choose to enter that relationship, form that union, male female, which establishes the compelling state interest. The state has no interest in a same sex relationship, if it had such an interest would have manifested itself long before now, quite possibly it would already exist before now, rendering this debate moot.
Lets take their DOMA ruling as a template. I am sure that your position on the issue was addressed by at least (probably many) of the briefs; that congress was acting constitutionally when it enacted DOMA for the reason you posit. Gee, it would seem that by mandating the federal government recognize same-sex marriages as valid and legal doesn't bode well for your side of the issue.