I wouldn't put too much stock in this survey. Results are highly dubious based on the source of the data. Any valid study would provide at least some background on how the results were determined.
"but City Data does not give the source for the list’s information"
Tennessee only has 2 counties listed on this survey and having lived there I can tell you that seems extremely off. Could be wrong but I imagine that it's more that the majority gun owners there (and probably in other counties in the south and west) knew better than to answer truthfully whatever survey or questionnaire that city-data.com got their information from.