No Baptist, Presbyterian, or atheist has also sued the Catholic Church for refusing to administer the Sacrament of Matrimony upon them, and religion IS a protected class. In fact, priests have also refused to marry two Catholics in their first marriage if they don't follow all the rules first.

I don't see this as an issue that needs "compromise."

As long as the state confers certain legal rights and benefits (including tax) as well as the responsiblity of a legal contract upon married couples, then the state gets to define the terms of that contract, and who can enter into it.

But if a church raises marriage to the level of sacrament, then the church gets to define who can receive that sacrament in their church.  We don't get to make the rules for anyone but ourselves.

In other words, render to Caesar.