Let's get something straight: Pride and Prejudice has nothing to do with racial prejudice. (If you want to read about that, Shmoop has plenty of options.) Jane Austen is a white lady talking almost exclusively about white ladies. (Love ya, Jane!) But all forms of prejudice are based on the same principle: you pre-judge somebody based on one most likely irrelevant fact, and you refuse to change your opinion based on actual, observable fact. It's the opposite of rational, liberal-minded thinking—and we don't mean liberal in any political sense. We mean liberal in the way Austen (and other writers of her time) used it: open-minded, willing to change your ideas, and interested in facts rather than opinions. You know—exactly the opposite of prejudiced.
In Pride and Prejudice, prejudice is a worse sin than pride.
Austen associates prejudice with vulgarity. No matter how wealthy or how high-ranked someone is, prejudice lowers a person's character.