All races are social constructs, but the degree to which they're harmful social constructs to self-ID as is variable. There are few good reasons to be angry with someone for identifying as maori or Haudenosaunee, for example. And getting mad at someone for identifying as black would be big time victim blaming and unproductive. But white? It was invented 500 years ago, Europeans already had less bad cultural identities, and it was a direct justification for many of the worst atrocities in history. And white people have garbage culture like lawns anyway.