The mistake that economists make is to essentialize a claim that is purely contingent.
Let me try my best to explain it.
That author contends that Marxists see no difference between free enterprise and special privilege. This is, at its most basic, incorrect.
Marxists can certainly admit (Chomsky has said as much) that free enterprise can exist without special privilege. Of course, two individuals can engage in free trade, and an individual can begin some form of enterprise. There is no necessary connection between free enterprise and privilege; the two can exist separately.
Marxists make the point that, given our cultural and economic history, there's no such thing as free enterprise (this is a general statement and by no means accounts for all business start-ups; but for many, and for the largest). Free enterprise, in the course of Western history, is most often the triumph of privilege over those who do not possess equal opportunity. "Free enterprise," experienced by perhaps some individuals, is only ever "free" at the cost of the prohibition of the less fortunate.