Now, I am not the first one to point out the fact that libertarian (in fact, all liberal) arguments are circular in that they assume libertarian (liberal) premises to reach their conclusion. It was, in fact, Alasdair MacIntyre who first convinced me this is so. So imagine my delight when I discovered a libertarian, Geoffrey Allan Plauché, who had denied libertarians made these circular arguments, completing a lap around the NAP in the space of a single paragraph, and doing so in addressing... Alasdair MacIntyre!
Now, what MacIntyre claims is that liberalism is not the "tradition-neutral" umpire it claims to be, but is itself a tradition, a tradition intolerant of other traditions, and one that will use force to bring them into the liberal order. What does Plauché make of MacIntryre?
"What MacIntyre is ultimate objecting to is the prohibition on violence and other forms of initiatory force. Is this the sort of community tradition he has it in mind to preserve? Perhaps he will reply that if communities are not allowed to enforce their traditions by aggression or the threat thereof, then they will not last in the face of competition. If this is the case, however, then they must not have been as valuable to those who abandoned them for alternatives. Who is MacIntyre, or anyone else who wants to preserve a particular community or tradition, to coerce others into conforming?"
Let's say I live in a old, tight-knit community. (As I happen to do.) And let's say the life of this community is being threatened by the construction of huge high-rise apartment buildings that will bring hordes of transient strangers pouring in, people with no ties to the community, no sense of its values, and no interest in whether or not it survives. (They'll be living in Greenwich in five years.) So my neighbors and I decide to prevent construction of one of these monstrosities by sitting ourselves down (quite peacefully) at the construction site. Per Plauché's "principles," we are engaged in aggression, and when the property owner calls in cops with tasers and billy clubs to clear us out, he is not!
So, when a community acts peacefully to protect itself, it is engaged in "violence." And when the liberal social order responds with violence in order to break up all resistance to the total dominance of market values, that is called "self-defense"! Of course, if we first accept liberalism's counter-intuitive definitions of what constitutes aggression and what constitutes defense, then we will no doubt find that liberalism is perfectly peaceful, and all other traditions are engaged in "aggression" in trying to survive. So Plauché illustrates MacIntyre's point beautifully by running a lap around the NAP himself.
UPDATE: And notice what Plauché assumes is the only reasonable test for whether a tradition should survive: "If this is the case, however, then they must not have been as valuable to those who abandoned them for alternatives." Traditions must allow themselves to be judged by the ultimate liberal criterion of goodness, the market test!