Let me just say that we can argue specifically about these two historically opposed systems (i.e. capitalism and slave-based economy); but let's also keep in mind the possibility that these aren't, or shouldn't be, our only two choices.
I know that Dak's theory basically holds that anything other than free-market economics is slavery, because it relies on some kind of centralized political machine to guarantee it. The problem with politically guaranteed economics is that there will undoubtedly be some form of dehumanization/exploitation/manipulation in order to ensure some kind of status quo. In the minds of the free-marketeers, any bondage at all constitutes a flaw in the system, and thus it deserves to be done away with.
So to address those two points, Grant, I think a radical free-marketeer would say: "Capitalism may result in dehumanization committed by individuals against each other. Any politically-organized system will inevitably result in dehumanization in order to prevent the possibility of dehumanization by individuals. This is a double-standard."
My question would be: is the enslavement of vast quantities of individuals even possible without some kind of strong, centrally organized political structure? Free-marketeers would argue that it is not, or at least not for an extended period of time. They would claim that if individuals in a free-market attempted to exploit the labor of others for their own economic gain, their venture would soon collapse due to either the impossibility to sustain a slave base without a politico-military establishment, or would face rebellion when its slave base grew too large.
In short: government isn't justified to prevent slavery, because slavery prevents itself; and furthermore, government involvement necessarily involves slavery.
Do we agree with this? I'm not entirely sure. I think that prolonged slavery is possible in a free-market system, if the economic institutions grow large enough. In time, economic institutions may even take on the role of political ones. This is where the lines begin to blur for me, and I have some other ideas/theories on this, but I'm going to save them for later because I feel like we have enough to discuss already.