Friend Andrew Coyne speaks up on behalf of Justin Trudeau's post-Boston Marathon remarks to Peter Mansbridge. Coyne: "I don’t say he offered much deep thinking on the subject: much else that came out of his mouth was vague, incoherent or both. But I didn’t hear much that was terribly objectionable, either."

OK, let's review why these remarks resonated so badly.

1) Remember, Trudeau was interviewed bare hours after the bombing. As he himself acknowledged: "Now we don't know now whether it was, you know, terrorism or a single crazy or, you know, a domestic issue or a foreign issue, I mean, all of those questions."

That's a good moment for a responsible leader to stop talking. If you don't know what happened, don't opine - much less commit yourself to any specific course of action.

2) Ignoring his own caveat, Trudeau then rushed ahead to reach his own unfounded conclusion. "But there is no question that this happened because there is someone who feels completely excluded, completely at war with innocents, at war with a society."

Yet in fact many terrorists are thickly embedded in social networks. Marc Sagerman, a former CIA psychiatrist, studied 172 individual jihadist cases and found that the single strongest predictor of the decision to join an Islamic terrorist group was having a friend or relative join first. At the time of his interview, of course, Trudeau did not know whether the killer(s) was or were jihadists. But he didn't know they weren't either. So it was a bad time to say "there was no question" about a conclusion about which there were sure to be plenty of questions.

3) Friend Andrew rightly condemns those who after 9/11 used the language of "root causes" to enlist the atrocity for their own political ends, be it to condemn Israel or call for more foreign aid. Justin Trudeau was doing just the same thing. In his speech announcing his leadership bid, Trudeau had identified "social exclusion" as one of the social ills against which he was campaigning.

Confronted with a question about a mass murder, Trudeau rummaged through his inventory of old speeches, and produced his pet issue as the "root cause" of an event about which in fact he knew precisely zero.

4) Trudeau spoke in the passive voice, about people who "feel excluded." It's possible to feel excluded for no good reason at all. Yet the implication lingers, it is that if people "feel excluded," somebody is excluding them. It's easy to draw the inference from Trudeau's words that he thinks the real culprit in cases of terrorism is this unknown excluder, not the unfortunate victim of exclusion who merely detonated the bomb that was somehow prepared for him by vaguely oppressive social forces.

In Justin Trudeau's comments on the Boston attack, we see a worrying formula: first, emphatic certainty ("there is no question"), expressed (as Andrew notes) vaguely and incoherently, all in service of an idea that is objectively wrong. Overconfident and mistaken: that is not the stuff of which successful prime ministers are made.