Libertarians of all stripes would be well-served to abandon the term "free market". I know it's near and dear to a lot of them, and I get it, I do: the words should hardly be controversial -- who among us can deny the value of "freedom" and "markets"? (well, many can and do, but that's neither nor there). There are a few reasons the phrase has lost all useful communicative value:
1) Many people misunderstand our governmental and economic status quo. They see our system as a fight between "capitalism" and "regulation" -- "capitalism" being a poorly defined/understood bogeyman: a sort of Hobbesian corporate state of nature, in which evil corporations run amok in a battle royale, dragging society and the environment down with them. Therefore, "Free Market" to them does not mean what it does to most libertarians. It means the absence of the regulation keeping this nightmare scenario from unfolding -- a precarious balance only barely kept in check by the unflagging efforts of the modern progressive.
2) The term has been coopted by conservative/right-leaning politicians seeking to "privatize" elements of government function. Though they use the term "free market" to justify and earn the sympathy of their constituents, the ultimate goal is not a free market, but mere profiteering. Any politician seeking or in office who claims to want to limit government and promote freer markets is at best disingenuous, as the advocacy of free markets is unlikely to be accomplished via legislative fiat. As Steven Teles pointed out in last week's Econtalk, most attempts at privatization only further the entrenchment of a social/"public" function of government (with a few more hands in the till, to be sure):
Some of the largest consulting firms, especially around here in the Washington, D.C. area, their primary and in some cases the exclusive purchaser of their services is government. And I think some of that's come from the fact that conservatives thought that if we actually, even if we are going to perform, if some function is going to be considered to be social, if we can push it out into the private sector then that private sector will become a lobby for further privatization. But in many cases those private contractors become a lobby for the continuing socialization of the function, so long as they are the ones who end up getting the benefits.
3) Consequently, the term has also (fairly) been vilified by leftists who look at the consequences of purportedly "free market" policies, and see nothing but exploitation of the system. However, they also, unfortunately, use the term as a pejorative to denote/signal to their constituents that corporate profiteering via privatization is imminent -- to the detriment even of potential governmental policies that could actually help encourage a truly freer market.
If libertarians truly want to change the minds of others, they should abandon this unproductive phrase. For all the reasons above, it does nothing but conjure up an aura of harmful exploitation. Instead, focus on what is (for some) at the heart of libertarian ideals: opposing coercion/aggression. "Anti-aggression" is a phrase likely to get you a lot more traction in any discussion with your average statist, because it focuses the conversation on something which libertarians share quite deeply with most liberal statists: the deeply held belief that aggressive violence is harmful. From here, a genuine conversation about the trade-offs we make with respect to freedom is much easier, or at least it cuts to the heart of fundamental disagreements much more quickly. Waving the flag for "free markets" might score points with people that already agree with you, but it will do nothing but confuse and confound potential allies who grossly misunderstand your goals.