Hmm. The link doesn't seem to work. Do you have an alternate?
I'm not a sociologist or anything, but from what I understand about dry counties, is they tend to be in more rural areas, where poverty tends to be an issue. So it's not surprising meth tends to be a problem in dry counties. Meth is some pretty scary shit and the just as scary heroin seems to be picking up steam again too.
Edit: Here's a map of Kentucky with county breakdown for alcohol laws. It's about five years old, but it still paints a pretty good picture.