The "non-aggression principle" is basically a propaganda con by libertarians, though.
The way this works is that they take their own favorite definition of personal property, and then re-define the word "aggression" as: "anything that violates my definition of personal property, and nothing else".
So, when a land owner shoots somebody who mis-stepped onto his land without warning, that is not aggression according to libertarians - if you really take them seriously.
Obviously, when you point that out to a libertarian, an endless game of shifting definition starts, much like how many discussions about the existence of god go with theists.
You are spreading FUD and misinformation. Shame on you. The non-aggression principle does not work like the laws of physics, so just because someone steps on your land, it does not give you the right to shoot them. You are arguing from absurdity. The non-aggression principle is about not committing force, fraud or coercion against another human being. It's really that simple. You may use force when someone is directly threatening your life. That's how it's been discussed in the forums and videos I've been exposed to. Stop holding principles regarding morality to the same standard as the laws of physics.
I certainly wouldn't endorse it, just pointing to it as an attempt to avoid the circularity of defining violence as "what the state does" and then defining "a state" as "the organization with a monopoly on violence".
I do think it nonetheless ends up pretty entangled in the ideas invented by the modern centralized state, especially the ideas of "property ownership" and "a contract", which are supposed to exist in a sort of ethereal global-variable state separate from any facts in the physical world or local interactions. The modern state enables that fiction by maintaining a central property register backed by a cadastral survey, and a set of courts that enforce the abstract idea of a contract. Minarchists are perhaps more open about this dependence than anarcho-capitalists are, by just directly asserting that the state should exist solely to operate and enforce a property register and contract law.
You're probably right, there's definitely a spectrum of libertarianism.
And it's not as if libertarians are entirely crazy. It's healthy to have some baseline skepticism towards authority. But it's also healthy to have some baseline skepticism towards market solutions. As usual, the best answer(s) are somewhere in compromise and in the middle.
I guess that ideas like the "non-aggression principle" are so alluring to some because they have a sort of superficial "intellectual purity" which that kind of compromising answer lacks.
The way this works is that they take their own favorite definition of personal property, and then re-define the word "aggression" as: "anything that violates my definition of personal property, and nothing else".
So, when a land owner shoots somebody who mis-stepped onto his land without warning, that is not aggression according to libertarians - if you really take them seriously.
Obviously, when you point that out to a libertarian, an endless game of shifting definition starts, much like how many discussions about the existence of god go with theists.
If you're interested in a well-argued and entertainingly written outsiders' perspective on this, I recommend Matt Bruenig. Here's a starting point: http://www.demos.org/blog/8/21/13/fun-times-libertarianism