Proper application of the Constitution would have to show the Constitution as granting a right to everyone to marry. It doesn't.
But frankly, the whole subject is old. On to the Supreme Court.
You have identified a sort of weak link here. However, remember that constitutional dicta (pl. of dictum) and the cases they arise from don't happen in a vacuum. There has to be a "case or controversy" (the Article III constitutional term) in which there is a dispute over something -- whether Fred the Perp did in fact burglarize the hardware store the last Sunday in May; whether Dapper Dan did indeed get trusting Penelope Pureheart into a compromising situation; whether your deed or mine to that parcel of land we both claim to own is the valid one; whether State Statute Sec. 94(c)(3)(a) does in fact deprive Joe of a right guaranteed to him by the constitution....
In this case, the right to marry is not enumerated in the Federal constitution. However, this gives rise to the possibility that, say, Idaho could in fact ban marriage -- no one would be permitted to legally marry within the state, and it would give no legal recognition to marriages contracted elsewhere. I think everyone would agree this is absurd. So Chief Justice Warren said, in
Loving that the right to marry is one of the fundamental rights in a human society. Note that. while the particular case in point simply challenged an anti-miscegenation statute, SCOTUS did not simply rule that blacks and whites may marry -- he was forced to look at the basic idea, and asserted it as an unenumerated right. There are only a few of them spelled out, and none that depend strictly on the Ninth Amendment, which asserts that such rights do exist.
What this decision does, however, is to examine the provision of California's state constitution put in place by Prop. 8 in the light of the Fourteenth Amendment. As you probably are aware, this forbids any state from depriving any U.S. citizen of life, liberty, or property without due process of law, or from denying them the equal protection of the law.
Equal protection jurisprudence is fascinating, and complex. But there is a bottom line that says that any law must have a rational basis -- an that rational basis cannot be your or my religious beliefs, no matter how firmly we hold them to be true. It has to be something understood to be true and rational by all people -- the conservative Christian, the liberal atheist, the libertarian humanist, the objectivist Jew....
Back to the 'right to marry' again -- if it means anything, it means the right to marry the person of your choice, presuming she (or he) is agreeable. Saying that your right to marry means you have the right to marry or not marry a particular person or small group of people, regardless of your own wishes, is contrary to American social principles. Arranged marriages have never been common in America, and are effectively defunct these days.
Well, okay, so people have the right to marry the person of their choice. Now, we look at the slippery slope stuff. Chester the Molester does not have the right to marry his 12-year-old girlfriend because the state has a legitimate interest in protecting its youth. The hillbillies have no right to marry their sisters, because the state has an interest in protecting society against the deleterious results of incest. The nutball who wants to marry his car or his blue-tick hound is not trying to marry another
person. These are limitations with a rational basis. And there is a presumption of constitutionality of the state law which must be overcome by the person challenging it.
Now, the court said, if some people have the right to marry the person of their choice, and that is limited only by laws with a rational basis, what is the rational basis behind prohibiting two homosexals from marrying each other? And the judge sought testimony with the intent of establishing what rational basis, if any, there was for that prohibition. He wrote a long, thorough opinion carefully reviewing that testimony in search of such a rational basis -- and did not find it. He even quoted Justice Scalia on the subject.