Hmm.  An interesting, if somewhat terrifying, conclusion.  I've not seen good data on this in a while, but a lot of anecdotal accounts suggest that evangelicals are doing quite well among upper-middle-class white folks.  Yes, they target lower-class folks, but their base, as it were, appears to be at least partially upper- to middle-class.  I've also seen a reasonable amount of anecdotal evidence that suggests fundamentalists do quite well among lower-class folks.  In short, I guess, I'm asking - have you seen some numbers that bear out this theory?