Behold the perils of invoking moral equivalency - even, or perhaps especially, when some of the events in question are separated by 800 years.
During a speech Thursday at the National Prayer Breakfast, President Barack Obama leavened his condemnation of the Islamic State's recent atrocities with a word of warning to his fellow Christians who wish to conflate the militant group's actions with Islam as a whole.
"Lest 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," the president said. "In our home country, slavery and Jim Crow all too often was justified in the name of Christ."
Murderous extremism, he continued, "is not unique to one group or one religion. There is a tendency in us, a sinful tendency that can pervert and distort our faith."
The comments prompted an angry reaction - bordering on apoplexy - from many on the right.
Washington Post columnist Charles Krauthammer called the president's comments "banal and offensive" and "adolescent stuff".
"Christianity no longer goes on Crusades," he said on Fox News. "The story of today, of our generation, is the fact that the overwhelming volume of the violence and the barbarism that we are seeing in the world from Nigeria to Paris all the way to Pakistan and even to the Philippines, the island of Mindanao in the Philippines, is coming from one source, and that's from inside Islam."
Others, such as conservative radio host Rush Limbaugh, took issue with the president's contention that IS is not reflective of Islam as a whole. "Sharia law is the present day threat to individual and civil liberties all over the world," he said. "Sharia is not a narrow cult. Sharia law is Islam."
But what about the Crusaders? Since they aren't around to stick up for themselves, Powerline Blog's John Hinderaker comes to their defence.
"There was nothing wrong, in principle, with the Crusades," he writes. "They were an appropriate (if belated and badly managed) response to the conquest of the Holy Land by Islam. Did marauding 11th century armies inevitably commit outrages? They certainly did. In fact, that still happens today. But the most unfortunate thing about the Crusades is that they failed."
He goes on to note that the body count from the Inquisition "would hardly make a good week's work for Boko Haram or IS" and that the anti-slavery movement in the US had a decidedly religious bent.
"Slavery might well be widespread today if it were not for Christianity," he says.
The National Review's Jonah Goldberg builds on this theme.
"There's a very important point to make here that transcends the scoring of easy, albeit deserved, points against Obama's approach to Islamic extremism (which he will not call Islamic)," he writes. "Christianity, even in its most terrible days, even under the most corrupt popes, even during the most unjustifiable wars, was indisputably a force for the improvement of man."
It's difficult - almost impossible - to believe the president and his staff didn't anticipate the reaction his words would generate. The question, then, is why he picked this particular fight.
The president could just be poking the right-wing bear, says the Christian Science Monitor's Peter Grier. More likely, he continues, he's trying to counter the view - held by Limbaugh and others - that the US is at war with Islam as a whole.
Instead, Grier says, the president - like George W Bush before him - wants to frame the conflict in terms of a fight against "individuals who use distorted versions of faith as a weapon".
But perhaps there's more than just the religious component at play here. As Juliet Eilperin of the Washington Post points out, Thursday's speech is in keeping with Mr Obama's penchant for challenging what he sees as the US public's lack of self-reflection when it comes to their past sins and their place in the world.
"Obama's remarks spoke to his unsparing, sometimes controversial, view of the United States - where triumphalism is often overshadowed by a harsh assessment of where Americans must try harder to live up to their own self-image," she writes. "Only by admitting these shortcomings, he has argued, can we fix problems and move beyond them."
Chauncey DeVega, posting on the Daily Kos, goes even farther, drawing a direct comparison between IS's murder of Jordanian pilot Muadh al Kasasbeh and the gruesome "spectacular lynchings" of the late 19th Century, which involved hanging, and burning, blacks accused of crimes.
"We cannot overlook how the United States has conducted master classes in violence and barbarism both before, during and since its founding … and yes, much of this violence was against people of colour whose labour, lives, land and freedom were stolen to create American empire," he writes.
Perhaps a rational dialogue about religion extremism throughout the course of history is possible - but it's increasingly clear that it's not a conversation this president can start and that this US political environment will tolerate.