To understand much of our language, Gnorts would have to already be aware that our words and symbols gain meaning from how they're used, and you couldn't, for instance, determine that a swastika is offensive (in the west) by its shape alone.
In this case, the term "colored people" gained racist connotations from its history of being used for discrimination and segregation - and avoiding it for that reason is the primary principle at play. There's also the secondary/less universal principle of preferring "person-first language".
Like the paragraph quoted above: it's just so blatantly obvious what's wrong with turns like "considered particularly enlightened", or "there are no underlying principles" that I find it hard to believe that the text as a whole sounds so friendly and convincing, unless you stop and think for a second.
I wish I could write like this about whatever mush is in my head.
Similarly, Graham almost certainly already has strong opinions on the basic premises of this essay. Thus, the process of revising and polishing his essay to make it readable and compelling doesn't help him spot any of these obvious critiques. As you quoted, he believes the people advocating "people of color" over other terms have no principles. Thus he can't apply their principles to his own essay and anticipate their criticisms. Based on how he describes "wokeness," he seems to think are generally unprincipled.
Neither he nor his reviewers are equipped to analyze the substance, which is why it can be stylistically strong but substantially weak.