Switzerland was in no position to take sides even if they wanted to. Bad example. What if England chose to remain neutral in WWII?
To answer your scholastic question about the needs of human nature I'll refer to Maslow since he is the simplest to argue. As long as physiological, safety, interpersonal, and esteem needs are met, people will thrive. It should be our goal to create a community that fosters these to the best of our ability. The rewards for doing so will be ever improving technology.
Switzerland's a perfect example of exactly how a libertarian nation or AnCap region would handle being surrounded by warring nations. "Well, I suppose my people would have to shoot twice."
OK, now, how does libertarianism fail to meet those needs?
Countries that were conquered during WWII were looted. Switzerland was not a military threat, but would have been conquered and looted as soon as resources were available. Yes, sometimes you have to "shoot twice" that's life. The French Underground was a good example. They never really stopped resisting. So I guess you would never choose violence as a course of action? Ghandi would have been a better example for you, although nowadays they too are a member of the nuke club.
Libertarianism is not based on science. I have no reference for defending it. You have not posited a clear specific argument where AnCap is sustainable. The Wikipedia article mentions historical roots to related philosophies, but that's like saying we have a mission to Alpha Centauri planned because we went to the moon. I think your philosophy has a lot of development to do and probably requires a technological breakthrough of some sort before it should be attempted.