Categorization/generalization could be helpful in helping us make decisions, especially on issues that currently cause harm towards other people. Obviously, not all rural people are racist, but racism does tend to be worse in rural areas. There's a theory that a large part of it is the lack of racial diversity and engagement between races in rural areas. People are not as exposed to people of other colors as much in those areas, that they never learned to care for people of other races.

Some interesting difference between people perception on races in rural vs urban areas:
http://www.pewresearch.org/fact-tank/2013/08/28/the-black-white-and-urban-rural-divides-in-perceptions-of-racial-fairness/

ps: Race is really just some social construct anyway, but it's unfortunate that there are existing racial demographics that are treated unequally depending on the areas. Once people someday stop thinking in term of skin color and races, then we could stop worrying about it.