When I was in middle school, one of my friends told me, "My family doesn't believe in microwaves."
Though I myself also have never bought and owned my own microwave, I still think my friend's choice of wording is wrong. "I don't like microwaves," or "I choose not to use microwaves because I think it's gross to eat reheated leftovers" are both acceptable expressions, but "I don't believe in microwaves" seem to imply either that (1) microwaves do not actually exist or (2) microwaves are falsely rumored to have deity-like properties.
So, when I say, "I don't believe in free markets," I don't mean that I deny their existance. I mean that I want to deny that free markets have numinous god-like attributes.
Free markets are generally a good idea, but they are nothing more than a fallible system. Free markets are not God or god. Free markets will not save us from our excesses. Free markets do not guarantee good results or a stable economy.
Free markets should be our servant, not our master.
Stanley Fish has a great article about neoliberalism here. Neoliberalism can be defined as a quasi-religious belief in free markets.
Let me put it clearly: I believe in God. I believe in love. I believe in the bright future of the human race. But do I "believe in" free markets?
Let those who worship free markets be the first to see the image of Baal fall flat on his face.