I agree with you that ethnicity as a determinant for one's behavior is pretty idiotic. It's one of my pet peeves.

I do however disagree with you that bananas are yellow on the inside, they're white. I guess we'll just have to agree to disagree there.

Don't fight about boundaries of colours! Everyone loses. I've nearly come to blows with good friends about the boundaries of pink and lilac.

In this situation, where the professor-guy's definition of a WASP is probably more behaviour-based than the technical, ethnical definition, then a technical objection, like Gilda's, will come across as irrelevant to him. I guess. So maybe you could've asked him for his definition of a WASP, and then worked from that. And also, he was probably embarrased because you called him out on labelling you, which is in itself a nasty thing to do. Labelling, that is.

I second the vote for white. At best, it's cream. Yellow? I think not.

I have 100 angels dancing on the head of a pin...

Let's stop splitting hairs about colours. Pip is right. It's way too subjective.