This is one of my huge pet peeves. Even liberals, progressives, socialists and communists criticize capitalism for its reliance on market forces. But capitalism is not about free markets. By definition, capitalism is about privileging the owners of capital to restrict markets, to make markets not free.
The fundamental concept of capitalism is not "whatever happens in a free market is good by definition." It can't be, because a free market is a market where large-scale socially constructed coercion doesn't exist. But coercion does exist, and it can't be arbitrarily hand-waved away except as a purely theoretical concept.
The fundamental idea of capitalism is rather clever (and an improvement, I think, on previous political systems, especially feudalism): power, i.e. the privilege of restricting markets, should itself be allocated using market forces. However, it suffers from the flaw that those allotted power have the power to restrict the markets that allocate power. They will inevitably allocate power to those of their own social class, i.e. people like them, in typically superficial ways.
All political systems relevant to present-day reality will be coercive in some sense. Coercion itself is not bad: the only way to believably bind myself to a promise is to make that promise in a social context that will coerce me to keep it. Otherwise, I have the temptation to betray that promise later for my own individual benefit.
It may be possible to create conditions where it would be psychologically impossible to break a promise, even without coercion, but that day is far in the future. The next step is not to abolish coercion, but to ensure that coercion is employed to humanistically to enforce a higher-level rationality in our social constructions, i.e. that coercion is employed for the benefit of human beings, not to reify and privilege some abstract ideal.
[lakercat9 notes correctly in comments that the following is an overstatement in the original. I've amended it to be more precise.]
Not only is