This professor’s behavior was irrational at best, deranged at worst. Even if you exclude the racial element of the quiz question and subsequent reaction, it is completely baffling. I read this story and see her escalating it at every turn. I would think that a professor would be excited to see a reaction to a question graded as incorrect as polite as yours (i.e. “I thought the answer should be x, can you explain why it is y?”), as it indicates engagement with the material and a desire to learn.