The vast preponderance of classical music is wholly fixed in arrangement and form (exceptions being the Sawkins style bass lines - see Sawkins -v- Hyperion - and certain aspects of organ music) whereas the core of jazz is improvisation.

As opposed to, say, trad folk.

Does it not occur to you that someone can consider Louis Armstrong, Vivaldi and, say, Nikhil Banerjee as absolute geniuses on an equal musical footing with each other without any hint of patronisation or closet racism?

I can't speak for Adam Smith, but this has nothing to do with the term "black classical music". The question is not how genius these guys are. It's how the term "classical" is being (ab)used.