The President is supposed to uphold the people's Constitutional rights. If all humans are to be considered persons deserving of equal treatment under the law, then supporting the right for a man to marry another man or a woman to marry another woman is the least one should expect of the President of the United States. The rules of religion should have nothing to do with the government and the law.
Though this is a positive step in the constant fight for universal equality, I don't think I particularly trust politicians. There's always something else behind every decision. Few if any say things out of the kindness of their hearts. This may be honorable on its face, but to be honest, this could be the thing that loses the election for him in the contentious red states. Especially if he starts talking a Constitutional amendment or something.
But my opinion? No, not at all. He's fine with me. Long as he doesn't like, declare himself emperor or something. But then, that's kind of what I'm hoping for any President, so...
--sd-7