The sins of the father and all aside, libertarians are not necessarily isolationists. I'm not sure I'm a good representative in this regard myself. Based on the information and understanding I had at the time, I was in favor of the invasion of both Iraq and Afghanistan. I have never, in my defense, been in favor of "nation-building". I saw those invasions as part of an overall plan by the Pentagon to isolate and pressure Iran. Iran has been a problem since Jimmy Carter sold the Shah down the river and let an ally became an antagonistic Islam "republic" -- you know, sort of like Obama and Clinton did with Egypt. Libya was less of an ally but certainly not any longer a threat. The surrender of WMD's by Gaddafi had been one of the few positives resulting from our Iraq invasion.
I was wrong to trust the military and the political class in this country, and the longer and more I am treated like a potential terrorist myself lest the government be accused of profiling by the very people who need to be profiled, the more I regret that trust. Did we need to retaliate against Al-Qaeda for the WTC and Pentagon attacks? I think we did, and I think most libertarians understand that now and understood at the time, though it is ever more evident that the response path chosen was not the best alternative.
Libertarians, especially the small 'l' variety, are no more exclusively isolationists than neo-cons are exclusively warmongers. It's a different philosophy and approach to an obvious problem.
Here's Simon how starts out:
Being an early frontrunner for a presidential nomination is not always a good thing and Sen. Rand Paul acknowledged as much the other night on Greta Van Susteren’s show. He must have channeled his inner Nostradamus because not more than a day later a man named Putin made his move on Ukraine. He could end up Paul’s worst nightmare.
This invasion could be a nightmare for libertarians like Rand Paul, but it could also be a wet-dream for neo-cons. As inconvenient as Putin's invasion of Crimea is for some, it is extremely convenient for others.
The next thing somebody will bring up is the treaty we have with Ukraine. What they are talking about is the 1994 Budapest Diplomatic Memorandum that acknowledged the territorial integrity of the newly-formed Republic of Ukraine in exchange for surrender of the nuclear weapons within its boundaries. The signatories of this diplomatic memorandum were Russia, the United States and the United Kingdom. This was not a treaty ratified by the Senate, and, as the linked article states, the Memorandum can be used as justification for actions by the U.S., but it hardly compels our country to take any action.
It's signed by Russia. Russia is just as "obligated" to abide by it as we are. Ukraine did their part in surrendering their nukes. Looks like a local dispute to me. National interest trumps a diplomatic memorandum. It is not in our national interest to get involved in any way, though it could that the business of war would benefit some economies, financial institutions, and international bankers.