Why is Beheading Reckoned Worse than Death by Drone Strike?

Do not underestimate the impact of Good War Mythology. The U.K. and U.S. firebombed Dresden, Cologne and Tokyo, inter alia, during World War II. The U.S. dropped atomic bombs on men, women and children in Hiroshima and Nagasaki. A crime against humanity? By no means! Don't you see? Now the Germans and Japanese are prosperous and forward-looking and "free"! Just like us! Yes, Virginia, you can perpetrate mass murder to advance the Greater Good! Just make sure you do it on behalf of the Anglo-American Empire! Otherwise you're just one of those evildoing, good-for-nothing Terrorists!