These quotes also reveal the authoritarian xenophobia and absolute arrogance that underpin both ideologies. For these extremists, peaceful coexistence with mainstream society is intolerable. For them, resisting modernity is an ordained mission equaled in importance only by the necessity to impose their own agenda.

Their death-cultism is now on full display in Iraq. About a week ago, ISIS released a video of their latest exploits. The grotesque hour-long footage shows ISIS capturing Iraqi police officers and then shooting them as they kneel down and wait to die. In slow motion, ISIS regales us with terrified prisoners digging their own graves, and with assassinations.

The ISIS videographers crow in the background. At one point, the camera records a gang of masked men who are slowly interrogating a police officer for propaganda value. Then, two of the terrorists jump on the officer and behead him, slowly, as he flails and struggles. The next scene shows his decapitated head sitting upon his torso. This is the world they seek: a “holy” kingdom of death.

But consider Iran — more strategically astute than ISIS, yes, but no less evil. Whether in its support for Assad’s chlorine-gas attacks in Syria or in its own numerous atrocities at home and across the world, Iran has no qualms about using death and fear as political weapons. A case in point is Iran’s plot in 2011 to blow up a crowded restaurant in Washington, D.C., in order to kill a Saudi diplomat. Former CENTCOM commander James Mattis tells the story here.

Of course, it isn’t only ISIS and Iran. In Yemen, fighters from al-Qaeda in the Arabian Peninsula (AQAP) film themselves massacring unsuspecting villagers. In Kenya, Al-Shabaab has just murdered fans watching the World Cup. In Nigeria, Boko Haram slit throats and kidnaps children. (A celebrity-led hashtag campaign has thus far rescued no children.) In Beirut, Iran’s ally Hezbollah casually murders its democratic opponents. These cases are just a few from the swamp of Islamic terrorism.