C3PX said:
It doesn't really have anything to do with people from the UK, or some irrational dislike of redheaded people they might have. Zombie is from Canada I believe (could be mistaken), and I have heard people in the states use that expression my entire life. It isn't intended to suggest that red headed people are weird or anything, it means the exact same thing as the term "black sheep" the one that doesn't quite fit in, looks differently from the rest, etc. i.e. a family has four kids, three with brown hair, but the oldest child from a previous marriage has red hair and looks different from the others. There are no anti-redhead sentiments here.

Odd. I'd never heard that phrase in my life. (Perhaps Minnesotans don't really use it much.)

Otherwise, on the surface the phrase sounds "anti-redhead" to me. Are you saying that you have firm knowledge that the predominant use of it has had no negative meaning to any degree? (I must question that assertion in the absence of precise evidence.)