1. Marriage in the USA is driven by State Laws, and it is governed by State Laws.
2. Churches have no innate authority to marry individuals, only that authority which is given to them on a case per case basis. A church cannot officially marry two individuals without a valid marriage license, and just because the Church married two individuals before, does not give them the authority to marry further individuals, without a valid STATE marriage license. Also the CHURCH does marry people, effectively the Pastor/Priest/Minister … has been given the authority to marry these two people, and is merely representing the State. They may also represent the Church, but the Church may not officially marry people, unless they are representing the state.
3. Churches do not hold the definition of marriage in their hands. That is up to a State and it’s laws. States may not discriminate, about who may be married, about much of anything. Churches may determine who can be married in their buildings, (which they do have a lot of large buildings,) and filter those they feel are reasy for marriage, etc.. Churches are allowed to discriminate.

Now as far as churches go, let them discriminate until the cows come home. We allow for private groups to discriminate freely, (the KKK doesn’t allow Black members, Skin Head groups apparently require you shave your noggin, etc…) In fact I would like to see this brought up more, please remember it is their right to discriminate, and they should be allowed to exercise their rights, just as you and I are able to.

States on the other hand are not allowed to discriminate, with some exceptions. No matter how much you want to, the State won’t let you marry your sister, borther, mother, father, 1st cousins. Those are perfectly reasonable, as you just assume that married partners are going to have sexual relations. However most States until the past 25 years or so, have not had any laws on the books denigrating the rights of Homosexuals. These laws are discriminatory, and they must be over turned.

In short, Religious beliefs of what constitutes a valid marriage must be allowed to persist in the Churches. We have no right to enforce that Churches must perform marriages of people they find unacceptable for marriage. At the same time we must insist that our States remove laws from the books, which discriminate against the rights and beliefs of those who want to be married.

p.s. While I do not approve/disapprove of Gay marriage. I do believe that States that do not allow it, will sell themselves short, as married couples pay more in taxes than do single people, over the same period of time. This is especially true if the couple has children, either adopted or conceived as part of the relationship.