I'm afraid the history of the word is clearly tied to classism against impoverished and lower-income rural white people. There has been an attempt in the past few decades to associate the word and low-income rural white people in general with racial bigotry, but I would argue that that is itself an example of classism -- racial bigotry is a big problem among white people of every level of socioeconomic status, not just low-income white people. If you mean to talk about bigoted white people, I would urge you to just use that phrase. I would characterize the use of the word "redneck" among some poor and low-income rural white families as an attempt to reclaim a word that has been used to marginalize them -- the same principle being at play among some black people who try to reclaim the N-word. I would argue that just as people who are not black should not in general use the N-word, folks who are not impoverished or low-income rural white people should not in general use "redneck."