This explains prejudice because it is having a misguided attitude towards something because of a bad example. In this case Anne is saying Jews get the bad end of the stick compared to christians, because when one Jew does something that isn't so good all Jews are placed in that same unfair box.
Other examples of prejudice is saying all black people are ghetto or rude, all white people dont like black and are racists, all rich people are materialistic. .