If you asked the difference between Evangelical and Mainline churches in America today, most in the media would frame the difference as a political one. Evangelicals are Republicans, Mainline Christians are Democrats. But this is not the defining issue. The question that is at the crux of the division between Christians lies in the answer to this question: how authoritative is the Bible in your life?
There has never been a generation, never a time or place, where Christians haven’t had to come to grips with whether they will bow the knee to the prevailing norms or whether they will serve God alone. And how do we know what God wants? His word to us. When push comes to shove, when the Bible calls me to believe something or act a certain way, will I believe? Will I obey?
The reason, then, that sexuality has become a litmus test for what “camp” you are in has little to do with political leanings, but rather this question of authority. I truly don’t mean to be glib when I say this (and it may well be good fodder for a post later), but there just isn’t a strong biblical argument for sex outside of a heterosexual marriage to be anything other than sinful. That’s not, of course, to say that some don’t try to make such arguments, but rather that those arguments are inevitably grounded in a progressive ideology.