Because some people in government are now hostile to marriage as God defined it, in order to protect godly marriage we must remove the power of the State to define and regulate marriage. Then anyone will be perfectly free to enter into whatever relationship they want. However, they will not be able to call upon the police power of the state to force me to recognize a “marriage” that I know is theologically illegitimate and morally repugnant.
If we remove government from marriage and return it to the private sphere where it came from, lesbians can still marry
each other, but they won’t be able to use government to force me to sell them wedding cake or artfully photograph their “marriage”. They will be free to do as they please without being able to coerce anyone else about their private
affair.
I am willing to discuss this as a desirable path philosophically, but it will never ever happen in real life. Put simply, Democrats will not go for shrinking government power, and if GOP is too weak to support status quo man woman marriage, they are not strong enough to overhaul the whole institution.