The problem is that "keeping the government out of the church's business" is not the goal of the religious right when it comes to gay marriage. They want theocratic rule and the criminalization of what they see as sin. If both sides agreed on the principle of separation of church and state, most battles over LGBTQ rights would've been over long ago.

Separating the legal concept of unions between individuals and the religious institution of marriage would be almost as unpalatable to many evangelicals as fully legal gay marriage, because they'd rather outlaw homosexuality altogether.