How does Ms. Gates comments about democracy contradict what we have seen happen in Maycomb?

Miss Gates tells that students that Hitler is able to treat Jews poorly because he is the government. She goes on to teach the children that the US is a democracy and Germany is a dictatorship. In her explanation of the differences between the countries she says that "Over here we don't believe in persecuting anybody. Persecution comes from people who are prejudiced." What is ironic in her explanation is that people, including herself, are prejudiced towards African Americans. She is forgetting that Tom Robinson is being persecuted because of the prejudices the townspeople have.