Marsalis recently slammed trumpeter Christian Scott because his rhythm section didn't swing, and therefore it wasn't jazz. In at least one interview, Scott listed a bunch of jazz players who were apparently not jazz under Marsalis' definition of jazz.
It's interesting that anyone would distinguish between the way Marsalis is in private and what he espouses in public. I would have assumed that his public persona is not like an actor who plays a role in a movie; he chooses what comes out of his mouth, and is not working off of someone else's script.
Outside the world of jazz, more people have actually heard original music by Miles Davis than by Wynton Marsalis. Isn't it funny how someone who is less influential assumes, for whatever reason, that he can decree what is acceptable... especially for an instrument he doesn't play? *laugh*