Dies3l -- I for one appreciate the nuanced approach you are taking in trying to facilitate communication in this thread. I do have some points to make relative to your posts.
First, a national referendum as you suggested would in fact be unconstitutional, as a SCOTUS decision would not, because of the wording of the Constitution. Specifically, the Tenth Amendment. Congress has those powers, and only those powers, granted it in the text of the Constitution -- including the Interstate Commerce and Elastic Clauses, and Section Five of Amendment XIV. Marriage is a prerogative of the States; all Congress can do is to mandate an even unified standard by which each state gives legal recognition to marriages contracted under the laws of another state. It may not ban gay marriages nationwide (except by Constitutional amendment); it may not provide for a referendum on the subject. It's ultra vires -- beyond Congress's legal power.
On the other hand, if the argument that gay marriages are legal under the Equal Protection Clause is valid, then (1) it is emphatically the business of the courts to protect that right, just like any other right. If the Town Council of Atheistville passed an ordinance making all prayer illegal in town, the courts would throw that out as a violation of the First Amendment. (Amusingly, the ACLU would be among the first to institute that suit. The same would hold with reference to gay marriage. Earlier, some (male) CF member commented to another (gay mle) CF member that they had equal right already: the right to marry the consenting woman of his choice. I found it interesting to note that nobody observed at the time that Texas Lynn and Enemy Party have, or should have, the same right under law if we as Americans do in fact have equal rights -- each should have the right to marry the consenting woman of her choice. If they are not equal before the law with the commenting member and the person he addressed, then there is in fact an equal protection violation
But (2) Congress would also be empowered to make a legislative finding that the Equal Protection clause is in fact implicated, and in consequence they could adopt a national standard permitting gay marriages, by their power under Amendment XIV, Section 5. The reverse, however, banning gay marriages, is not an exercise of their enforcement power under that article, and unsupported by any other constitutional provision.
The interracial marriage decision, Loving v. Virginia, in place 40 years this summer, is very much on point. The Chief Justice was called on to determine if Virginia's law barring whites from marrying non-whites, and the reverse, was in fact illegal. He found it to be a violation of the Equal Protection Clause -- because he established, by judicial fiat, that marriage is a fundamental right, presumably one of the unenumerated rights. From the perspective of both the "defense of marriage" crowd and the pro-gay-marriage crowd, it's a brilliant move. Would it be legal for a state to completely abolish marriage, prohibit any legal marriages within its bounds? Everyoine, I hope, would say, "of course not!" Hence it is in fact universally perceived as a fundamental right. Not interracial marriage or gay marriage, mind you, just the basic concept that John and Mary are free to marry under reasonable limitations (not close relatives, of age, single....). And that being the case, to prohibit two persons who wish to marry from marrying on the basis of race violates the Equal Protection Clause.
In passing, the polygamy issue brought up earlier is invalid. The essence of a marriage contract as seen by law is to commit oneself exclusively to one other person. To say that already being married constitutes a bar to contracting another marriage is to recognize that basic commitment.
