Who cares how smart your enemy is? You don't need to be intelligent to be dangerous.
The author clearly doesn't understand the point of asymmetric warfare. Even if people want to laugh at the fact that 50% of Afghani suicide bombers don't kill people, 50% DO kill people. Suicide bombers aren't doing a cost benefit analysis of their efficacy and then deliberating on whether they're going to blow themselves up or not. Their job is to sow terror, and pierce the idea of safety.
In spite of any of the points mentioned in the article, it's still possible to recruit suicide bombers to go blow themselves up for an ideology that's insane.
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I do honestly believe that we should point out the absurdity of suicide bombing. But the absurdity is not a question of their efficacy, which is undeniably a winning strategy if you've got the man power to throw at it. The absurdity of suicide bombing lay in the ideology, and the goals one seeks to achieve by blowing oneself up.
This article is at best naïve, and at worse, dangerously ignorant and besides the point. Fight ideas.