'Free market' does not necessarily imply no government. Most libertarians wholeheartedly agree that bringing harm to another, either directly by initiating violence or indirectly by fraud, is wrong and should be legally punished. That is the core of living in a civilized, democratic nation.
The idea that some people should be able to make laws to tell other people what they can or cannot do in completely voluntary arrangements is in fact a return to tyranny, however well-meaning it may be.