[Some] libertarians are also notoriously guilty of pretending that their favorite kinds of coercion aren’t. Threatening force to deny another person use of one’s land, or one’s house, is coercion. A system of private property is a system of coercion. It may be justified coercion. It is justified coercion. But then the question is: What justifies it? The coercive protection of property is justified because people do better with it than without it. If people do better in a system that defines rights to property a bit less strictly, and coercively guarantees an economic minimum, then that is justified coercion.
Too right. At this point simple libertarians appeal to the distinction between self-defense vs. initiating force. But as I explain here:
Property-claims initiate force against others. The original privatization unilaterally removes others' access to what would otherwise be a common resource. That's an aggressive imposition of harm on innocent people, without their consent. We then threaten aggression against them, merely for wanting to use the resource in the same (peaceful) way as we do...
Again, one's attempts to claim exclusive use ("ownership") of a resource may well be a reasonable limitation to (attempt to) impose on others. But that doesn't change the plain fact that the claim to property is an (attempted) imposition. And of course it's logically necessary that their initial claim to ownership occurs prior to anyone else's interfering with their property -- otherwise it wouldn't be "their property" yet!
So there's really no possible way to deny this. It's a plain statement of fact: to claim a right of exclusive use (i.e. a "property right") over a resource, is to limit the options available to other people -- including people who have not yet done anything to you. This is a form of "coercion", in the value-neutral sense of the term.
Simple libertarians have difficulty appreciating this, because they think of property as a 'given', a basic feature of the natural world, rather than a human imposition -- or "social relations of constraint", as Cohen aptly puts it. These constraints are so thoroughly internalized that they fail to even notice them anymore.
So step back, and try to imagine seeing things from an alien's anthropological perspective. The alien has all sorts of physical and psychological concepts, but no explicitly moral ideas such as 'rights'. All he does is observe what is the case; he makes no judgments about what ought to be. So when he visits Earth, what will he see?
Bob and Sally are stuck on a desert island, with a banana tree. Bob gets there first and claims it as his own -- maybe he mixes his labour with it a bit, waters and nourishes it, whatever you like. Later, Sally goes to eat a banana, and Bob stops her, pushes her back. Who aggressed against whom? From the value-neutral perspective of the alien, the answer can only possibly be that Bob was the one initiating force here.
For libertarians to offer a different answer, they must not be using 'force', 'aggression', 'coercion', 'liberty' etc. as purely descriptive, value-neutral terms that even the alien could understand. They must instead be loading their moral assumptions into the concepts, effectively collapsing 'aggression' into 'unjustified aggression'. These moralized concepts presuppose libertarianism, they therefore cannot be used to argue for libertarianism on pain of circularity. This is why simple libertarianism is more accurately called 'propertarianism'. What's philosophically fundamental to the view is property rights, not liberty.
Anyone who truly takes liberty itself as a basic concept (rather than redefining it in terms of some other moral conception like property rights) must acknowledge that property rights can infringe on liberty. And once you make that step, the only sensible response is to assess the various institutional systems on offer, including those which render property subject to some degree of redistribution, and opt for the one that best promotes human flourishing (or whatever we think is ultimately good).
'Philosophical libertarianism' thus looks to be incoherent. There's simply no avoiding ubiquitous coercion (understood in a value-neutral way). So we can't get anywhere by taking that as our fundamental evaluative principle. 'Propertarians' instead treat property rights as their fundamental value, but further reflection reminds us that it is not rights themselves that fundamentally matter, but the people they are meant to protect. And so we end up with utilitarianism, at least at the fundamental level. One may, of course, still be a 'political libertarian' in the sense that you think libertarian policies will tend to best promote the common good. But anyone who thinks capitalism is intrinsically or necessarily just is simply confused -- or am I missing something?