Watch his work and be enlightened.
Government, by definition, is a legal monopoly on force in a given geographical area. Always has been, always will be. The Founders were brilliant men, but the American experiment has failed miserably; not due to lack of vigilance, but by design. The government which governs least will ALWAYS become the largest. Why? Because the capital derived from free association between free men produces unparalleled production and innovation. It's only a matter of time, then, until the monopolized force steals the product of the labors of enterprise at gunpoint.
As for your argument about for-profit prisons, it's simply asinine. Prisons are the worst of a fascistic economy; a collusion between government and corporations. There are no prisons without law. There is no law without the elite ruling class known as "government". In a free market, individuals have the CHOICE to subsidize methods of deterring crime. Would YOU support a local enforcement agency who was willingly killing and/or locking up innocent men? Of course not. Can you stop funding the current corporatist prison system without men with badges and guns locking you up? Again, of course not.
Minarchism is nothing more than deadly compromise.
"The state is the great fictitious entity by which everyone seeks to live at the expense of everyone else."