Good post and good read. I would say he is half right--it is tribal and it is also religious, although the Shia-Sunni divide is in many ways tribal in its origin, the Shia seeking succession via "blood" or tribal lines. In his defense, he does state this with the critical sentence
"The enemy is tribalism articulated in terms of religion."
but he fails to follow up on the thought, which is really essential to understanding the AO.

The best sentence in this entire article is
"you can't sell "freedom" to tribesmen any more than you can sell "democracy."
It's funny (sad funny not ha ha funny) that this same article could be titled It's the Clans, Stupid, dated Oct 1992 (3) and we could be discussing Somalia.

Best

Tom