Postmoderns put great value on "authenticity"--being real, not putting up a facade, or a mask, not play-acting (which is the original meaning of the Greek word that became our English word "hypocrite"). They don't like it when people seem all right but are actually pushing a "hidden agenda."
Rednecks share some of the same attitudes, they just express it differently. They might say a certain person is "puttin' on airs" and even issue the warning "Don't git above your raisin'."
When I was thinking about starting my own blog and the idea for its title hit me, I googled the term "postmodern redneck" to see if anyone was already using it. Found various places where the two words were in the same sentence or paragraph, a few people who did refer to themselves in that way, but no one with the blog title at that point. The other thing that came up was a Wikipedia article about "rednecks"--yes, there really is one. It included material about the origin of the term--one theory is that it goes back to red scarves worn around the neck by 17th-century Scottish Covenanters, and was brought over to America by Scottish and Scots-Irish settlers (my mother's maiden name is Burns, by the way). The article also included a quote from a Professor James C. Cobb of the University of Georgia, essentially regarding a redneck as a man "who is what he is and doesn't give a damn what anybody thinks."
If that ain't authenticity, what is?