We conservatives like the free market; that declaration ought to surprise no one. But we also know that it is not and never will be truly free. Why is that?
Human imperfection, for starters. We aren't perfect, and it is silly to believe that a perfect system can come out of less than perfect people. Every human construct will be flawed and there's no getting around that. Markets, being human constructs, will not always lead to the right or best result. Of course, we think that free markets are the best there is at getting beyond error. Yet that doesn't mean they always will. As one of chief arguments against government interference in the economy is that too much is going on for governments to efficiently regulate, it applies as well that in free markets too many people and too many decisions are involved for every single effort to work out well. Yes, markets will organize themselves to a certain degree. But not exactly right and not necessarily in everyone's best interest in every single instance.
Then there's that pesky fact that not every economy in the world is free. True, that is not the fault of free market economics. Yet is another reflection on that pesky idea that people aren't perfect. Simply telling folks that they need freer markets won't lead to them. Government interference alone will see to that, and the simple assertion that open markets are better won't convince everyone that they are. It may be honest disagreement, stupidity, power, or just plain obstinacy which prevents accepting the free market rationale. The markets will never overcome all such obstacles. As such, completely free markets will never exist. There's no point to pretending they will. There will always be interference in them; about the best we will ever have is to limit that through the political process the best we can.
Now we come to those pesky social issues which drive the more rabid free market enthusiasts mad. Not every human trade ought to be in the open market. An easy example is slavery, but it goes beyond that. Prostitution comes to mind, and of course the entire abortion industry is simply wrong. What we're leading up is this: merely because people could do something doesn't mean that they should. Some activities must be banned simply because they're so wrong that an enlightened society must not tolerate them. We can argue where the line should be drawn: that there is a line is another question. There is, and we must find (or at least get as close as we can) and adhere to any legitimate market parameters which exist.
Finally, and this comes directly from our third point, free markets are not the end all be all of human existence. Right and wrong are; doing what's right and avoiding what's wrong the best we can should be our goal. Even the concept of free markets itself recognizes this. Proponents essentially say that markets ought to be free because justice demands it. Yet once we say that, we are effectively arguing not for free markets but for justice. It appears that free markets are a subset, albeit a very important subset, of justice. That also makes it appear that justice can make demands of markets, and that markets not only cannot but should not be totally free.
The freest market possible market is the best market because it allows for the most possible good for the most people. Yet it would still be flawed, it would still commit error, and we need to realize that if we are ever to improve upon it.