FInally, Obama saying that gay couples "have a right" to marry is patently false. Under current civil rights jurisprudence, they don't. This would be like JFK saying that women "have a right" to an abortion in the 60s.

This is a poor analogy. Abortion was legalized under due process concerns, while schools were desegregated under the equal protection clause. The current issue is definitely one of equal protection, so desegregation is a better analogy.

Anyway, it doesn't matter, because people are not granted rights by the Court (you know, that whole "inalienable" thing). People are inherently free and the Court gets to sometimes decide what, exactly, this means under the law. That doesn't mean that politicians (or you or I, all of whom enjoy free speech) can't advocate for what they view as a human right. He has as much right as you or I to say if he does or does not view this issue as one of civil or human rights.

I didn't make a reference to schools, btw. I said Jim Crow, which is far more encompassing, and the Court didn't decide on. Jim Crow was ended by an act of legislation, independent of the courts, that LBJ lobbied for relentlessly. I don't know where you're possibly getting the idea that only courts can be the arbiters of what is and isn't a right. The Federal government could pass a law tomorrow making any type of marriage legal, which would automatically make all the state laws barring it null and void. The courts could then decide on the Constitutional legality, if it were challenged.

I know of very little historical precedent for the president making a public statement about how laws should be interpreted.

What else is there to executing the laws of the land? Its a constant interpretation. The executive branch has to set up non-specified regulations, decide which illegals to arrest, decide how forcefully it will pursue the war on drugs, etc, etc, etc. They make interpretations every day. (Remember the Bush memos about torture? The whole Bush Doctrine, for that matter?) The Court doesn't do this. The Court only rules on what is legally challenged, and they have no standing to arbitrarily say "this law is unconstitutional" without some party bringing suit.