It shows the concentration of ignorant, deluded, wicked, foolish, or oppressed
victims of obsolete mythologies in the United States, with the lighter colors being the most enlightened and the dark reds being the most repressed and misinformed. Oh, it's labeled as the frequency of religious adherents, but it's the same thing.
Myers received a lot of flak for his comments, which were probably more off-the-cuff than serious when he initially made them, but how can anyone refute them with intellectual integrity? The map itself depicted "religious adherents as a percentage of all residents,” and showed the highest percentages in dark red, lowest in light yellow.
The comments drew flak from the same atheists that tend to pussy-foot around with religion rather than confront it, but none that I saw offered a real rebuttal that went beyond the argument that we should respect others beliefs. One critic, not an atheist however, went so far as to call Myers an asshole, and stuck to the ad hominem route rather than logically refute the paragraph above. He later attempted to remove the post, but it would seem that the Scienceblogs web architecture has defeated that, since the post still remains.
Atheist Revolution has a post that deals with the finer points of the Myers quote above, but I’ll add that delusion is present among many in these regions. Moreover, a distinct lack in education correlates with many of these regions. Does religion promote lack of education or does inferior education promote religious beliefs? I suspect it’s a little of both with a feedback loop, but the correlation is obvious.