Hoppe says his theory proves that arguing for any political position other than libertarian anarchism is logically inconsistent. ... his theory is an a priori, value-free praxeological argument for deontological libertarian ethics. Argumentation ethics asserts the non-aggression principle is a presupposition of every argument and so cannot be logically denied during an argument.
This is just the transcendental argument for God adapted for libertarianism, isn't it?
Seems like it. I think it works if we're only talking about two people. But what if those two people are debating whether to bomb the residents of the next country over? How does that in any way presuppose NAP?
Isn't the NAP kind of empty though? If I'm hitting you, I may not be "aggressing" against you.
Not necessarily. Though I think if it is consistently applied, it ends up undermining the ancap position. After all, property is theft.
Stephan Kinsella already wrote a rebuttal of that way of seeing the NAP, but GC demolished both. Speaking of that bald man, an article needs to be written on Kinsella, too. He's less of a crank in that he doesn't buy conspiracy theories, but he's HHH's lapdog and he's sort of a cultist.
Austrian arguments often look logically airtight until you scratch the surface and notice how specious they are underneath. I can't even say that for this one, though. I don't even understand the justification Hoppe gives for jumping from rational discourse to the bits about homesteading and scarce resources. Perhaps this is omitted in the summary; it doesn't seem to be too informative.
As for Habermans, I always thought his ideas came from an overly idealistic rationalism, though I haven't read him in any depth. All my knowledge is second-hand from some historians I read who seem to love him.
The link you gave to the LvMI article outlines it. Notice the obligatory boilerplate "...and Liberty" in the title. Kinsella is such a clown; not many in the movement even like him. Also, check out the praxeological argument for intellectual property! What snake oil.