I'm pretty sure the Founding Fathers wouldn't have found an inalienable right to buggery in the Constitution, but it seems agreeable to you. "Gay marriage" would have been anathema. But again that is no obstacle for you to freely invent and overlook as desired.
The founding fathers also did not see a right to freedom for blacks, suffrage for women, suffrage for non-property owning white men, or mixed-race marriage.
Funny enough, most openly discussed the need for protection of minority (in the original sense) rights in a democracy. Given that they were at the forefront of "freedom for all" in the context of the norms of their time, it is fairly likely that they would support all of those rights if they adopted modern norms.
Either way, it's all very irrelevant. The founding fathers were very clear about both 1) the separation of church and state and 2) protection of minorities from majorities. These, combined with the 14th amendment and mixed-race marriage protections form a solid legal basis.