Human beings are a very genetically homogenous species, far more so than most.
Suppose you take a member of an ethnic group and compare them to two other randomly selected individuals, one from their ethnic group and one from a different ethnic group. The chances their genetic differences will be greater with one rather than the other is very close to 50/50. Ethnicity makes only a very tiny difference, the vast, vast majority of the differences between individuals have nothing to do with it.
/s (although I've seen that argument here before)