Late in his piece, I found a very interesting paragraph:
"When Moktada al-Sadr called for fellow Shiites to demonstrate against the American surge last month, General Petraeus wrote an open letter to the Iraqi people pointing out that such demonstrations would not have been permitted under Saddam Hussein, and asking the demonstrators to avoid violence. In the end, the demonstrations were limited in scale and peaceful, and fears that Sunni terrorists would set off a wave of attacks on the protesters proved unfounded."
First off, al-Sadr was calling for a demonstration against the American occupation of Iraq, not merely the escalation. Second, I found it very interesting that in a contemporary gathering of pieces on the march (From the BBC, Al Jazeera, UK Guardian and IslamOnLine) there's no mention of a letter, "open" or otherwise from Petraeus. If he ever wrote such a letter, it didn't come to the attention of anyone in Iraq or in the larger Middle East.
Did the followers of al-Sadr need to advised to avoid violence? There's no question there was a great deal of violence at the march, but all of the violence was directed against inanimate objects:
"Many in the crowds were seen trampling on and striking US and Israeli flags painted on the ground with their shoes, an act considered one of the worst insults in Arab culture."
But as Juan Cole points out:
"...some journalists are writing that al-Sadr called for violent attacks on US troops, the communique he released on Sunday simply says that Iraqi Army troops and Mahdi Army militiamen should not fight one another and should not allow the Americans to manipulate them."
Was the march reduced at all? Doubtful, as there were about a million Iraqis there. That doesn't sound like a march that was "limited in scale." It's not at all clear that the appeal allegedly put out by Petraeus, if there ever was any such appeal, had any effect whatsoever. I think this "open letter" of General Petraeus falls under the category of what Markos Moulitsas referred to as "making shit up."