You're completely ignoring the fact that we are speaking in terms of White Supremacy and not genealogy. If White supremacy didn't exist, and human beings didn't recognize race in social political terms, you'd technically be right. But in the current reality, you're not.
Once again I understand how white society may view them, my point is how those people view themselves and in turn we as a group should respect how they want to be identified and not just acquiesce to whites opinion just because they are the dominant society.