How does Tom Buchanan being racist affect the story ?

Tom's racism is just another example of his very superficial, entitled and just hateful personality. Tom is concerned with himself. The nonsense that spews out of his mouth is a reflection on his own insecurities and general ignorance about other people. The racism is just another way that he validates his own sorry existence. This story is all about the filthy rich of East Egg. Racism seems to give them some sort of justifications for their vapid lifestyles.