Given that one of the tenets of Libertarianism is the NAP and thus military should only be used for defense, are military guards for diplomatic posts an acceptable use? Personally I think they would be allowed since their primary mission is protection of the staff and not one of aggression but I figured I'd see what y'all think.
That would depend on if you are AnCap Libertarian or Minarchist Libertarian. A minarchist would argue that the post is necessary since government should only exist to resolve disputes and protect its citizens. AnCaps would argue that trade should be unfettered and that the post is unnecessary. That said, I haven't met many (if any) AnCaps who believe in communities or nations being isolationist since Capitalism can (and does for the most part) work on a global scale. Conflicts are part of human nature and can happen in any size community. I don't think any socio-economic system can prevent them from occurring.
I don't particularly identify with either of those labels. You might call me an anarchist or libertarian "without adjectives", sort of a pseudo-intellectual doomsday raider. It seems that capitalism works on a global scale so long as the community is globalized. Indeed, conflict is a part of human nature, and ultimately every large civilization to date has imploded after reaching a certain peak. No such thing as free lunch or world peace, y'know? Civilizations rise and fall, stocks climb and crash, populations boom and bust.
Socioeconomic politicking and international diplomacy aren't so much "unacceptable" as they are irrelevant. Global trade is the ebb of the tide, while some miscellaneous calamity will be our downfall. At least temporarily, until we bounce back. Until we just go extinct. This is no conspiracy theory, nor apocalyptic prophecy, just a noticeable pattern of events throughout history. Law and anarchy are two sides of the same psychosocial coin. Isolationist communities are somewhat inevitable, only give it time.
Withdrawing voluntarily from international relationships at a reasonable pace might just ease the shock of whatever bitch-slaps our species next.
Libertarian doesn't always equal anarchist. I was once a full blown anarchist, the kind that believed in every person for themselves/no rules, but as I've grown older I tend to identify with either AnCaps or Minarchists (depends on the day sometimes the week). I think humans need some sort of economic system in place and the capitalism is the fairest system in the long run since it can exist between two people or billions of people. That's not to say it isn't a flawed system because all systems are flawed due to an inability to fully account for human nature.
I think that isolationism can be advantageous but it can also be very dangerous. If you are trying to build up a strong community, being isolated allows the community to identify strengths and weaknesses of the individuals and adapt accordingly. However, isolation can also breed jealousy and suspicion in those who are outsiders as well as breeding suspicion of outsiders. For example, isolated tribes in various parts of the world have been known to kill outsiders who stray into the tribal areas and various groups of outsiders still try to infiltrate isolated tribes. Isolation tends fail because it doesn't nurture an important aspect of human nature: the quest for knowledge. Isolationism essentially puts an end point on that quest and while some are content to stop there, many others want to keep gaining knowledge and thus conflict comes back into play.
As I said before, I don't believe that any system is completely right or completely wrong, all are flawed and it's up to the individuals of the community to establish the best system for their community (except full blown Marxism/socialism, that just doesn't work and never will without changing human nature).
I must say I like that you're a free thinker.
I would argue that diplomatic posts themselves aren't really acceptable. Communities trade with each other, have any extended contact whatsoever, there will eventually be conflict for one reason or another. Nations should begin the process of isolating themselves, if the next bottle-necking event doesn't do it for us. Communities should only be big enough to prevent excessive incest.