A fellow free-market-oriented economics blogger, whom I respect but whom I won't name because I also respect Facebook privacy, wrote the following on Facebook:
I guess I disagree with standard libertarian view on this [ISIS]. Libertarians, like progressives, do not think that there are evil people in the world. So the theory of terrorism is that it is "blowback" caused by previous actions of the victims. A couple of counterexamples come to mind. First, we fought a brutal war against Germany in the 1940s, but we did not suffer "blowback" terrorism from them. Second Denmark was not a colonial power in the Middle East, but they suffered the most recent terrorist attack. This is an issue where one cannot rule out the possibility that the problem is a barbaric ideology, not blowback.
There's actually a lot of wisdom in his comment above. Although I think the 9/11 attacks, the ones that Americans still care most about, were "blowback"--that is, unintended consequences of previous U.S. government interventions abroad--it would be absurd to reflexively blame every terrorist attack on intervention by the government of the country whose people suffered the attack. This blogger gives two good instances in his comment above.
My criticism is of his first sentence above. I don't know of any libertarians who think there are no evil people in the world. And I've been a libertarian since 1968 and have interacted with, and read, literally hundreds and possibly over a thousand libertarians. So it would be hard to maintain that that is the standard libertarian view.
In fact, the argument against U.S. intervention in lands far from our own does not require that one think it will lead to blowback. It doesn't even require that one think there are no evil people in the world. It requires only one of the following two things: (1) that one think it is not the responsibility of the U.S. government to go, in John Quincy Adams' words, "abroad in search of monsters to destroy", or (2) that one think the government does not have information to do it well.
Those who deny (2) typically have what Hayek called, in the discussion of central planning, a "fatal conceit." They think the U.S. government knows way more than it does. I have detailed this, specifically in the case of ISIS, in my rebuttal of my Hoover interventionist colleague Richard Epstein.
In an earlier piece, I wrote about the fatal conceit in foreign policy.