Based on a message by Zawahiri, McCarthy has concluded that none of the sectarian violence in Iraq stems from internal problems.
He is not, as Lawrence Auster once called him, "the resident adult at National Review" (which essentially translates to "he is willing to say that Islam is bad)" He is delusional.
First of all, even if Al Qaeda fomented the sectarian fighting, this would be hard to do if there were not already sectarian tensions.
Secondly, after the events during Saddam's reign, the idea that there would naturally be no Sunni-Shia carnage without outside interference is MIND-NUMBINGLY STUPID.
Thirdly, even if Al Qaeda sparked the violence, only an idiot would think it not self-sustaining.
Fourthly, it is possible that the messages do no more than indicate that Zawahiri and Zarqawi knew that a civil war was going to happen (anyone familiar with the ethnic divisions of Iraq and who was honest worried about this) and wanted to take credit for it.
That is all.