This opinion was written by an African-American journalist who is more privy to the subtle expressions of white supremacy than you or I could notice. And yes, he can be partisan but he also rips on Biden's racism too, so he is a non-partisan whistleblower when it comes to racism in our culture.
The fact it would be considered "conjectured" and "void of facts" by a white audience is an indication of White folks not believing Black folks' and their observation concerning white supremacy and is in itself an indication of the white supremacists culture.
How does the author know what was in President Trump's mind?