I'm seriously not understanding the arguments of Dr. Pepper vs. Coca-Cola. They aren't even the same kind of drink, and DP technically isn't even really cola. It's very possible to like DP and CC at the same time, it doesn't have to be either or
That said, I would not say that ordering DP is "blasphemy" in Georgia. I know plenty of natives over there who like it. Some people simply love the original, but it is fair to say that Mr. Pibb is more popular over there.