What would you have done?

If you read oneof my previous questions you know of a girl in my cl that just gets on my nerves... well the other day me and one of my other friends were talking about a project on the AIDS epidemic in Africa... well this girl decides to take it upon hersel to make a comment and says that "All black people have AIDS".... i was good and controlled myself but i wanted to say something to her so badly.... but i didnt... now be totally honest what would you have done.