I'm not sure I follow what you're not buying into. Do you not buy into race even existing, or do you not buy into race being a measurable trait? First off, I think we need to look at the definition:
- Main Entry: 3 race
- Function: noun
- Etymology: Middle French, generation, from Old Italian razza
- Date: 1580
1: a breeding stock of animals
2 a: a family, tribe, people, or nation belonging to the same stock b: a class or kind of people unified by shared interests, habits, or characteristics
3 a: an actually or potentially interbreeding group within a species; also: a taxonomic category (as a subspecies) representing such a group b:breedc: a category of humankind that shares certain distinctive physical traits
4obsolete: inherited temperament or disposition
5: distinctive flavor, taste, or strength
I don't see how you can argue against definition 2 and 3(c). Is that what you're doing?