Millions of Muslims have been killed by Muslims. John R. Thomson tallies up the dead. This cuts against everyone’s pet theory.
As a rough analogy, the Islamic World is in a period similar to the 30-Years War in Europe. Since the fall of the Ottoman Empire, there has been political illegitimacy and chaos. Civil Wars frequently break out and occasionally spill over onto non-Muslim countries. Eventually things will sort themselves out, but in the meantime, it is worth remembering at the big picture. The past decades have been the bloodiest in Muslim history and nearly all those killed have been killed by rival Muslims factions.