Yet sometimes libertarian and conservative critics of American foreign policy do sound as if they are shifting blame away from the terrorists — who are ultimately responsible for their contemptible actions — and toward the victims. The nicest thing that can be said about this is that it is not a very good way to change people’s minds about foreign policy.

It’s also possible to exaggerate the effects of blowback. Charlie Hebdo wasn’t the most hawkish magazine in the Western world. It did, however, publish pictures of Muhammad. That’s what the attackers said motivated their decision to murder the cartoonists. Apologists for these crimes argue publicly that there should be consequences to exercising free speech in this manner.

Denying or minimizing these facts doesn’t do much for the credibility of libertarian foreign-policy arguments. And it ultimately doesn’t sound very libertarian.

It’s not as if the reality in France is kind to interventionists. If people born in France can engage in such attacks, if it’s so difficult for a country of 66 million to assimilate five million Muslims, what are the prospects for Western nation-building within the Muslim world?