Because of this, and because no state can possibly require a religion to perform a marriage against its own tenets, I really don't see how any church or set of beliefs should have any bearing on who should or should not get married other than under their own auspices. I've said this before - Judaism, for example, forbids a marriage between a man and his ex-wife's sister (or his wife's sister, for that matter) in his ex-wife's lifetime. (Jacob married his wives before the Torah was given.) No Orthodox rabbi would perform this marriage. However, such a couple is and should be perfectly permitted to marry civilly. No synagogue has lost any tax-exempt status or been fined because of this.
If LDS or Orthodox Judaism or Catholicism or whoever do not want to perform gay marriages, this is their right and their privilege, and it would be wrong to require them to do so. But that has nothing to do with equality before the law. The right and penalities of marriage should be available to all consenting parties - anything else denies the equality of all adult Americans.