[chuckee]

It seems to me all it needs to assume is that genetic* ancestry/ethnicity matters - i.e. it has some effect beyond just appearance (if you think caring about appearance is illegitimate). Could you explain why all those other strict assumptions are necessary?

Edit: Actually, I've just noticed this question shifts us from "it's not happening" to "it's happening but it doesn't matter". Is that your claim now, and you're conceding that it is happening? Or would "it's not happening but if it did it wouldn't matter" be closer to your opinion?

*'Genetic' to separate it from the culture and customs that are also passed down through ancestry.