BEIRUT, Sept 8 — The brutal school siege in Russia, with hundreds of children dead and wounded, has sparked an unusual round of self-criticism and introspection in the Muslim and Arab world. "It is a certain fact that not all Muslims are terrorists, but it is equally certain, and exceptionally painful, that almost all terrorists are Muslims," Abdel Rahman al-Rashed, the general manager of the widely watched Al-Arabiya satellite television station wrote in one of the most striking of these commentaries. Writing in the pan-Arab newspaper Al-Sharq al-Awsat, Mr. Rashed said it was "shameful and degrading" that not only were...