First of let me say I liked your article, I am a big fan of JP myself which is why I read it.
The reason why I commented on your article in such a brusque way is because I could tell that this would be an issue which you would be unable to see the same as I would, and I wanted to see if you would respond.
Race is real, and a biological fact. The fact that the edges between racial groups are blurry and that the concepts of race we think of have cultural elements to them does not change that. When these discussions happen, one of the first claims made by those who, like you believe that race is not based in biology, is that because it is impossible to accurately quantify exactly who is white, or black, etc... That means race does not exist. But it is hard to say when a pond ends and when a lake begins. When does the afternoon end and the evening begin.
None of that means we say that day and night, ponds and lakes do not exist. This is why I made my comment. People like you are willing to admit that the progressives are wrong about the sexes, but you are unwilling to admit that they might be wrong about the nonexistence of distinct human genetic groups as well, because so many of the lies about the modern world rely on these ideas going unchallenged.
Unfortunately you seem to be yet another person willing to challenge acceptable thought only so far as pushing further won’t cause you to rethink the most important precepts which underline our world. Race may be fluid to a degree, but so is biological sex, and you had no problem disregarding the consensus on that issue.