Welcome to part two of Guy Rundle's mid-winter short course on the knowledge class. For part one, go here.
The principal objection to the notion of a knowledge class is that, well, capital still exists. Some people own the means of production, some people work for wages. There's a categorical difference between Mike Cannon-Brookes and a jobbing coder or graphic designer, even if the latter are better paid than a shelf-stacker.
The argument from "economic classists" (they're not all Marxists) is that the cultural divisions between non-knowledge and knowledge workers -- the shelf-stacker and the waged software developer -- are either confected distractions, or a degree of deflected economic class conflict.