In the context of Obama's long-standing remarks on Islam and terrorism, though, invoking the Crusades and the Inquisition are wholly unsurprising. What is more surprising is that he hasn't done this sooner.
Obama, for the duration of his presidency, has forcefully tried to separate Islam from what terrorists who claim that faith do, in the name of it. The most striking example was in September, amid the growing threat of the Islamic State, when Obama declared not only that the terrorists were perverting their religion -- as he has often said -- but that they were actually "not Islamic" at all.
"No religion condones the killing of innocents, and the vast majority of [the Islamic State's] victims have been Muslim," Obama said.
In recent weeks, Obama's critics -- and even some Democrats, such as Iraq war veteran Rep. Tulsi Gabbard (D-Hawaii) -- have cried foul that Obama will not refer to "radical Islam" or to terrorists as "Islamic radicals."
Obama, though, is not budging. And his comments on the Crusades and the Inquisition represent the latest ratcheting up in his quest to change how people talk about terrorism. He views Islamist terrorists as exploiting their religion; his opponents believe there is something about Islam that creates fanatics who are willing to carry out terrorist attacks.
For what it's worth, Americans used to sympathize more with Obama. But the rise of the Islamic State appears to be pushing things in the opposite direction. A Pew poll in September showed, for the first time, that 50 percent of Americans viewed Islam as more likely to encourage violence than other religions. Another 39 percent said it was not more likely to encourage violence.
This could be part of the reason Obama is upping the rhetoric. Words matter, and the way this issue is framed is going to go a long way toward determining how the "war on terror" will be waged. Moreover, the rise of the Islamic State -- along with the lesser-publicized Boko Haram -- has ramped up the debate over terrorism and its roots to the highest point since perhaps after Sept. 11, 2001. This is a key moment in defining the terms of the debate. Both Republicans and Obama recognize that.
Obama's critics believe he's being Pollyannaish about the nature of the threat and how it is inherently tied to Islam. Without recognizing the seeds of terrorism, they reason, how can you combat it?
Obama disagrees wholeheartedly with that characterization and thinks attributing violence to Islam is unfair and damaging to relations between Christians and the broader Muslim population.
It's perhaps the defining semantics debate of his presidency.