> Looking at just the legal aspects, in 1789 (and 1776) we did recognize that 'all men are created equal' and equal protection (and due process might apply too). From those rights flows the idea that a right conferred to some, such as marraige, should not be denied to others.

That language is in the declaration of independence, which has no legal effect. The Constitution explicitly creates a system where all men are not created equal.