The issue with the devil's advocate position is this. There's no such thing as an "ethnic" European. Race is a very recent sociopolitical construct, born in the 16th/17th centuries and initially used to justify English supremacy over the Irish and only later picking up connotations of skin color. The genetic differences between a Scotsman and a Spaniard are far larger than those separating a Greek and a Turk.

Pre-modern European tribes did not place an emphasis on race; it didn't exist yet. Nor did they care about protecting the nation or their national heritage, as the concept of nation itself took centuries to form millenia later and only started playing a major geopolitical role with the French revolution. This isn't to say the tribesmen were multiculturalists; they had their own cultures and were often wary of outsiders, but mostly for reasons of self defense. But the supposed desire for genetic homogeneity didn't prevent Scandinavians from raiding the French and British coasts, abducting women, and forcibly mating with them, despite their cultural and genetic differences.