I can't say I'm at all surprised. I've met Bible Belt Christians who literally think that the only religious protection the First Amendment offers is that you get to choose your own denomination of Christianity.
Without trying to play the racist card, I can't help wondering if it goes back to the slave owners before the Civil War. Before then, I don't remember reading about the South being any more religious than the rest of the country, but as the slavery debate heated up, many Southerners used Bible quotes to justify it. After the South's defeat, I remember reading that there was a sharp uptick in religious revivals, particularly in response to the harsh measures taken during Reconstruction.