Instead he issued a blanket attack on libertarianism — “a very dangerous thought” — and implied that its adherents are unconcerned about the safety of innocent Americans, without any suggestion that they might be right about anything. Like a drone strike, he came at the question from miles above the ground. Unlike the military, he used no precision targeting. He said nothing at all about any particular controversy over national-security policy.

Libertarians are an important part of the Republican coalition. Republican politicians frequently disagree with libertarians on issues, but a broad-brush attack will understandably anger them. And even Republicans who aren’t down-the-line libertarians share some of their concerns. Representative James Sensenbrenner of Wisconsin, for example, is a longtime supporter of the Patriot Act. He is, in other words, not a clone of Kentucky Senator Rand Paul. But Sensenbrenner also favored the amendment to rein in the NSA that the House narrowly voted down this week. These Republicans can be persuaded to overcome their libertarian instincts on many issues — but not by being told that they shouldn’t have these instincts in the first place.