The idea that some white people (normally white Protestant) have that whites are superior to other races because of the things white people have accomplished even though they themselves as a white person have accomplished nothing in life. These white supremacists are often white trash and are often from the southern part of the United States. These white supremacists usually have this belief because they are at the bottom of social ladder and they want to have someone below them. White supremacists think that just because they are a white all other things accomplished by white people are shared with themselves. They think that because another white person did something important that they themselves share that accomplishment just because they are of the same race.
Jim is a white supremacist. He believes in white supremacy. He believe he is better than everyone else because he is white and that there are lots of accomplished white people. But Jim himself is white trash, he lives in a trailer park, hasn't had a job in 5 years and is not successful in any way.