Simply because someone claims they believe in libertarian principles doesn't mean that they actually practice what they preach, though. Libertarianism is not unlike any other body of thought in that respect.
I think most of the reason "vulgar libertarians" exist (and yes, they do) is because of the frusteration some have with irrational prejudices against the free market. This, in many ways, is a valid concern.
Capitalism as it exists today has historically needed much intervention from the state to perpetuate itself, however, and coercion is something that libertarians are against (or are supposed to be against, in any case.) This makes up a lot of what Carson writes about, and is the most valuable, in my opinion. One only needs to take a stroll down labor history lane to see this.