I put this in the category of a big lie, trying to take advantage that we know them to be animals. This impresses me as a Psyops kind of fable.
However, these are the people who saw heads off, videotape the act and post the video on the internet. At a certain point, cries of, "They couldn't! They wouldn't!" become largely irrelevant. It's a plain fact that these people are capable of unspeakable atrocities. We know that. But we still haven't really accepted it.
"The recent stories of baked children came to mind. I asked if Abu Ali had heard about children being baked. Ali said no, he had not heard such a story, but he would not be surprised if it were true because al Qaeda had done so many crimes, such as cutting off a mans head, putting it up on a stick and parading it around town."
Michael is much respected for his reporting on the war. I just did a quick search and found this...it may not be the complete story.