In this particular case, while there does exist a set of alleles against which you can cluster populations in a way that maps roughly to the set of races we define socially, that only represents < 10% of the genetic variation across populations. Basically, that means you need to arbitrarily toss out > 80% of the dimensionality of your data for that clustering to meaningfully map against what we socially construe as "race".
This casts a large shadow on the idea that the genetic notion of "race" can serve as support for using the social notion of "race" as a means to treat anyone differently. You may be correct in the strictest technical sense, but the link is so tenuous that it can't really be used for anything useful.
"Race is a social construct" is a bit of a misnomer. The proper formulation should probably be something like "Race is only meaningful because we socially decided to make it so."