That's the thing -- "race" doesn't really have a biological meaning. If anything it's just a vague suspicion that certain people are inferior or "alien" because of their DNA, the breeding, or simply their cultural upbringing. Of course it's all invented tripe, and biologically speaking it's equally untenable (from a biological point of view) to think of Poles, Anglo-Saxons and Italians as being of different "races" than it to think of Africans or East Asians in those terms.

But racists aren't the smartest bunch, you know, so in fact that's pretty much exactly what they think.