Parrish, Walter Block recently argued in his debate over spanking with Stefan Molyneux that the basis of libertarianism is not the NAP, rather its punishment theory. I think the NAP is an important component of punishment theory, as I think Block does, too, but the reason he said that was because he views libertarianism as, apparently, a reactive legal philosophy. In other words, and in the context of torture, you can torture others all day long, but if your torture is unjustified, what can your victim do to you in response? What is a justified retaliatory action to your unjustified torture (a violation of the NAP)? That is, according to Block, the question libertarianism seeks to answer.
Personally, I would consider what the use of torture would do to me. I imagine it’s somewhat mentally or spiritually destructive to the torturer. That’s a cost worth considering along with whether or not the person you intend to torture is guilty of the crime you hope to uncover. Should I choose to torture, I must accept the consequences for my actions if I am wrong in my assessment of the torturee. I don’t know if I would choose to torture, but I can say that I would do everything in my power before that if I was absolutely certain of someone’s guilt of such a crime as kidnapping and the possibility of having my loved one safely returned to me.