Good point. But, I am not sure this is prejudice or racism. In any cross-cultural paring, there is bound to be stereotyping and ignorance. Especially at first.
Good advice to not be defensive. If your partner is defensive, it shows a lack of caring. Even if he thinks he didn’t misspeak, the fact that she thinks he did is what really matters. Don’t try to defend yourself. Rather understand why she feels that way.