This is a remarkably ignorant set of arguments. First, libertarians absolutely DO NOT believe that human nature is "fundamentally good." Human beings are so corrupt that they should never possess illegitimate power over others because they will invariably abuse it. This argument knows no introspection; it fails because it doesn't take into account that the Ruling Class are people as well, and are by virtue of their position more susceptible to corruption. While it is true that private exchange by mutual consent can bring about negative externalities, so do public-private exchanges. Critics of libertarianism love to vent around words like "market failure" and "failure of the commons." But there can be no heaven on earth, at least not through political or economic means, the marxists hope notwithstanding. And those things are vastly preferable to interventionism that eventually mutates into full-blown totalitarianism.
Libertarian philosophy is compromised by a number of flaws in the philosophical foundations of their philosophy; these errors are entirely due to their refusual to look at human nature as it actually is instead of what they want it to be.
A partial list of errors:
-The majority of people can understand the benefits of limited government and free trade (most people are stupid and/or ignorant)
-That their is no underlying biological wiring between the sexes or races that will cause them to favor tyranny over freedom
-That people will handicap themselves by principles of “justice” instead of amorally grabbing what they can in life (most people will rationalize any advantage they can attain for themselves)
-That Human nature is fundamentally “good”
-That Humans are a “blank slate” and are basically interchangable
-Based on the preceeding two premises- that the threat of force and fear of resiproisty is not necessary to keep the untermensch in line (it is).
-That other groups of people (governments) will play by the same nice rules that they want our government to play by
Ultimately, Libertarians take their native high intelligence and combine it with their do-gooder/moralist brainwashing and mirrorimage the the combination onto the rest of soceity while not realizing that they are the exception and not the rule.
As for his other arguments, they can be easily dismissed. Libertarianism is not synonymous with anarchism; there are rules, its called private property. And the Government still has role of preventing oppression and violation of the private property laws.
So, while this is probably the best that libertarian would-be critics have to offer, it is so spectacularly incorrect that one is forced to conclude that libertarians really don't have to face much of a challenge in the intellectual marketplace.