This is one Libertarian position with which I agree. The The alternative, courtesy of the 14th Amendment, is nationwide, state-sanctioned same-sex marriage. Let religious institutions marry people and let the state allow consenting adults to draw up legal contracts that control the ownership and distribution of assets. Eliminate distinctions in the tax law between married and single people.
It is incomplete, and that makes it incorrect.
The whole point of recognizing marriage is a legal protection for women bearing children.
As a pastor, can I engage in civil disobedience and just marry folks in the eyes of God? Sure. But, if I have a supportive governmental system that also wants to protect that marriage for rational reasons, such as because the nuclear family is the basic building block of society, then I’m enjoined by the Apostle Paul’s summary about good laws in Romans 13 to support such a good law. For about good government, Paul says “he is God’s servant to do you good”.