Now it's always possible for theorists to contrast a Utopian portrait of a free-market economy against the gritty and unwelcome realities of extreme socialism, just as it's possible for people on the other side of the spectrum to contrast a Utopian portrait of a socialist economy against the equally gritty and unwelcome realities of unfettered capitalism. Both make great rhetorical strategies, since the human mind is easily misled by binary logic: if A is evil, it seems wholly reasonable to claim that the opposite of A must be good. The real world does not work that way, but this is hardly the only case in which rhetoric ignores reality.
The problem with the rhetoric, however, may be stated a bit more precisely: however pleasant they look on paper, free markets do not exist. Strictly speaking, they are as mythical as hippogriffs.