Thanks for your reply. I'm not sure why it's being downvoted, perhaps your definition is too narrow and definitely not authoritative (and why should you care).
Post mortem: Yes, I frequently neglect that sense of anti-, and rebracket such compounds differently. I could go on in the same sense of manipulation on the word level. Is an anti-anti-anti-racist position tennable?
The problem is with using the word "Antiracist" as a label or name. There is a movement that tries to use the word as a name, but is a case of a wolf in sheep's clothing. This movement is attempting to rewrite history. To teach that, for example, Lincoln was evil, didn't do enough, and should be erased. This is despicable and destructive. McWhorter simply, rightly, calls them wolves.