Oh, I think that it has to do with the very clever way that certain money and power interests have worked to pit groups against each other.  When manufacturing jobs were lost, it was important to shift the focus of blame from the business interests to other groups who could be scapegoated:  Blacks (code words: crime and welfare fraud), war protestors, uppity women, immigrants...  It's much less uncomfortable to blame what ails one on those who are perceived as being different in one way or another than to place blame on those who one hopes will give one a job.