While it is sort of hard (not impossible) to think of many other reasons to vote for Al Gore, John Kerry, and John McCain, obviously such a measure can only catch racist Democrats. Most other rural areas (excempting the Upper Midwest) already are Republican anyways.
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Much of Appalachia was Southern Whig territory and anti-slavery at the time of the Civil War and has been so ever since. Thus it is no surprise to see Republicans still dominating in those areas.
The interesting phenomenon is those traditional pockets of Democratic strength in mining counties that were unionized at the cost of many lives that broke with tradition and went Republican this election.
I'm not sure if we can characterize Appalachia as racist to any greater degree than elsewhere in America. How could one possibly quantify such behavior and attitudes, and even so it would be much more difficult to ascribe the 2008 Presidential election returns to racist attitude?