If you were to engage in a debate about religious violence with your average high school senior, you might encounter the claim that the modern scourge of religiously-inspired barbarity attributable to those who consider themselves Muslims is no historical anomaly. They might contend that the Christian world engaged in its own form of fundamentalism at the turn of the first millennium when the medieval European world embarked on a campaign to liberate the Middle Eastern territories conquered by Muslim armies. Having erected a dubious moral equivalency, your interlocutor is likely to then insist that it is hypocritical for Westerners to scold the Muslim world for incubating a violent strain of Islam that has become one of the predominant threats to international security.

This was essentially the familiar argument President Barack Obama made at the National Prayer Breakfast on Thursday. After conceding that there will likely always be those who will seek to “hijack religion for their own murderous ends,” he reminded his audience that Islam is merely following a dark path forged centuries ago by Christians.

“Unless we get on our high horse and think this is unique to some other place, remember that during the Crusades and the Inquisition, people committed terrible deeds in the name of Christ,” Obama said. “In our home country, slavery and Jim Crow all too often was justified in the name of Christ.” Obama also denounced Islamic State terrorists for professing to stand up for Islam when they were actually “betraying it.” “We see ISIL, a brutal vicious death cult that in the name of religion carries out unspeakable acts of barbarism,” he said criticizing them for “claiming the mantle of religious authority for such actions.”

Entering into arguments over which great religion holds the most defensible claim to moral purity is often a waste of effort. What is noteworthy in Obama’s comments is not his attempt to establish an equivalency between Christian and Islamic violence, but that he has undermined his oft-repeated claim that ISIS and its cadre of supporters are unrepresentative of their faith.

It’s strange that so few see the contradiction inherent in this assertion. The president, and many of his allies on the left, frequently trip over themselves to emphasize – correctly, as it happens – that ISIS’s acts of brutality are not archetypical Islamic behavior. The insurgency’s most recent atrocity, the immolation of a captured Jordanian pilot, is apparently a violation of Islamic norms according to even Koranic scholars in the Middle East.

But to assert this and in the same breath suggest that Christianity was also a violent, expansionist religion a mere 800 years ago is a contradiction. Why make this comparison if ISIS is not representative of Islam? Isn’t the concession in this claim that those who commit acts of violence in the name of their religion, regardless of whether those acts are supported by a majority of coreligionists, that they are representative of their faith? Therefore, by perfunctorily nodding in the direction of a moral equivalency between Christian and Islamic violence, isn’t the president invalidating his own claim that ISIS, Boko Haram, Ansar al-Sharia, al-Qaeda, Jemaah Islamiah, Abu Sayyaf, and a host of other fundamentalist Islamic terror groups are agents of a violent strain of the Islamic faith?

A tired liberal shibboleth holds that the strain of violent militancy that is self-evidently more prevalent among Muslims today than among other religious adherents is not historically noteworthy. This is not to say that Christians, Jews, Buddhists, Sikhs, &c. are incapable of violence, though that must be plainly stated in order to satisfy the willfully obtuse. The president’s decision to link medieval Christian violence committed in the name of their faith to the atrocities perpetrated by Islamic terrorists today, however, has eroded the foundations of his argument that religion plays no role in the global war against Islamist terrorism.