PHILADELPHIA — The beheading of American journalist James Foley by the Islamic State in Iraq and Syria, or ISIS, has rightly provoked global condemnation of the insurgent group and its horrific tactics. Yet it has also led to a disturbing return of the moralistic language once used to describe Al Qaeda in the panicked days after the 9/11 attacks.

In an eerie echo of President George W. Bush’s description of the global war on terrorism as a campaign against “evildoers,” President Obama described ISIS as a “cancer” spreading across the Middle East that had “no place in the 21st century.” Secretary of State John Kerry condemned ISIS as the face of a “savage” and “valueless evil,” while Britain’s prime minister, David Cameron, called the group “barbaric.”

There is no question that ISIS has committed thousands of grave human rights violations against civilians in Iraq and Syria, and that many of its most gruesome acts, like the execution of Mr. Foley, constitute war crimes. Anyone with a conscience is disgusted by their brutality toward not just Mr. Foley but the thousands of Iraqi and Syrian civilians whom they have killed, raped and even buried alive.

It is natural to want to condemn this organization and to do so in harsh language that fully expresses our revulsion over its tactics. Indeed, condemning the black-clad, masked militants as purely “evil” is seductive, for it conveys a moral clarity and separates ourselves and our tactics from the enemy and theirs.