Once upon a time when fornication laws were enforced, a marriage license was a license to have sex, and if a woman wasn't married and had a kid they took the kid away and god forbid a white woman had a black kid (I'm thinking Gone with the Wind here)
Well all that has changed, we don't need a license to have sex, marriage licenses are largely irrelevant. People should be able to sign a piece of paper like a contract, have it notarized or have their priest/pastor/rabi etc sign it and it should be recognized by everyone for all purposes. The state really does not have any business licensing marriage or regulating sexual activity. If you want to enter into that marriage or union with someone of the same sex or with multiple people who really cares.
The US is based on freedom and individual rights. If you want to join a church and live by their rules you can, you can limit yourself in anyway that you want because you are free to constrain yourself anyway you want and you can call it morality if you like, if that pleases you, you have that right as an individual. And if a group of you get together and want to excludes others from your religious club then good for you, you should be able to worship anyway you want. But what you can't do is enforce you beliefs on others who choose their own path designed on their freedoms and their individual rights.
After all, why should your rights and freedoms be protected when you choose to use them to deny others their rights and their freedoms. When the people in the US wake up and realize this, the US will be a much greater nation than it already is and it will be a lot closer to the ideals found in the constitution.
So go ahead and join a crazy cult where you get your nuts chopped and your "wife" has the cult leader's kids, that's your right and I say good 4 U.