[GraniteStateConservative]

Incest as a non-violent sexual practice among consenting adults is constitutional, but incestual marriages can be banned because governments can regulate contracts. The whole notion of contracts are based on that the state will make them binding, so states (of the feds) can choose which contracts they want to stand behind. Homosexuality is the same way. Private moral repugnancy has NOTHING to do with constitutionality. We're not a theocracy.

[William McKinley]

Incest as a non-violent sexual practice among consenting adults is constitutional

I do not think you are going to find widespread agreement and acquiescence on this point.