Voluntaryism is not pacifism. Voluntaryism is the idea that all interactions should be consensual, but this does not imply an expectation that all interactions WILL be consensual. That's actually part of the point. By saying that all interactions should be consensual, we have a standard for knowing when violence is justified.
When the borders of an individual's body are breached without that individual's consent, it is that individual's prerogative to use force to repel the trespass. This is called self defense. The individual has this prerogative because the individual's free will is the best and most legitimate link to their body. This link is non-transferrable in that it was created by the process of conception, gestation and birth. We acknowledge this best link for the purpose of avoiding conflict among individuals over the scarce resource called "human beings".
When an individual uses their body to transform scarce, rivalrous resources into means that are capable of being used in the attainment of some ends, the individual subsequently has the best, most legitimate link to said means. Likewise, we acknowledge this best link for the purpose of avoiding conflict among individuals over scarce means. Unlike the best link between the free will of an individual and that individual's body, the best link between a controlled, scarce means and an individual is transferrable through consensual exchange.
When the borders of these scarce means are trespassed against without the consent of the individual possessing the best link, it is the prerogative of that individual to use force to repel the trespass for the same reason that it's their prerogative to use force to repel trespasses against their own body: they have the best link.
In some cases, individuals may need help from other individuals in order to transform scarce, rivalrous resources into means that are capable of being used in the attainment of some ends. However, individuals may not always wish to share the direct product of their combined labor with those who help them, thus they are willing to give up some other thing they value less and which the helper values more in exchange for their help. This double coincidence of wants is what makes consensual exchange mutually beneficial. All other things being equal, consensual exchange therefore constitutes a legitimate transfer of best link - or title - to the things being exchanged.
In some cases, individuals may need help from other individuals to forcefully repel a trespass. That it is a matter of necessity from the perspective of the individual requiring protection does not mean that other individuals are obligated to help them, thus they are not free to trespass against the bodies of others in order to compel protection, but individuals are still free to help them of their own accord or in exchange for compensation. An exchange of compensation for protection will only occur if the individual requiring protection values what he's giving up less than the protection he receives, and the individual providing protection values what he's receiving more than his own time and lessened state of safety. In some cases, the knowledge that the individual requiring protection is safe and that a trespasser isn't at large is payment enough for protection from the perspective of the individual providing it. This double coincidence of wants is likewise what makes these types of exchanges mutually beneficial.
Some critics, especially relativists, collectivists and leftists (but I repeat myself), may say that this arrangement is indistinguishable from how the men and women calling themselves government operate, but they are overlooking one very significant difference: everything done under auspices of government is underlined by an act of trespass in the form of taxation, and coercion in the form of credible threats of trespass. To equivocate defense against a trespasser with the trespass itself is to render the word "trespass" - and even the very concept of bodily integrity - meaningless. Such an equivocation would thus be logically incoherent.
Again, we acknowledge which individuals have the best link to controlled, scarce means for the purpose of avoiding conflict among individuals over those means. Given that trespass is a form of conflict, this best link can not be transferred through trespass. This is why we are able to recognize theft, murder, assault, rape and slavery as being morally wrong. When this best link isn't acknowledged, there is no means by which to differentiate victims from aggressors and no means by which to demonstrate damages or grievances.
The tyranny experienced by individuals living without acknowledgement of property rights would therefore be indistinguishable from the tyranny experienced by individuals living under the threat of violence posed by those men and women calling themselves government, especially since "government" is a euphemism for expropriation in the name of property protection, which is just as logically incoherent as conflating defense against trespass with trespass.
I'm Jared Howe! I'm a Voluntaryist hip hop artist and professional technical editor/writer with a passion for Austrian economics and universal ethics. You can catch my podcast every Friday on the Seeds of Liberty Podcast Network.