This attack was carried by al Qaeda, not Sunni insurgents (look it up if you don't believe me). Why would al Qaeda do that? Are they in a civil war with the Shiites, too? No. This bombing in Tal Afar, like many such bombings, was definitely not part of the civil war. Instead, it was an act of terror designed to provoke the Shiite militias back into the battle against the Sunnis. Do you understand the difference? The bombing is not an example of a retaliatory attack carried out by Sunnis against Shiites (that's the civil war schema). It is, instead, an example of Sunni al Qaeda trying to get Shiite militias to kill more Sunnis. And al Qaeda is doing that to further its jihadist objectives -- objectives that Sunnni insurgents do not share. I am just amazed that these virtually indisputable facts are not more widely appreciated.