It is their version of the Christian/Catholic Crusades that not only set out to conquer the Holy Land, slaughtering non-believers along the way. It also drove out and slaughtered the Jews of Spain, Portugal, Britain, and other European countries. It conquered and converted much of Africa, Central and South America, and spread into Asia. What was done on the name of Christ is now being done in the name of Mohammed or Allah.

There are a number of serious problems here.

-Conquering the Holy Land. Rather, Crusaders were trying to re­-conquer it, as Muslims had been waging war and slaughtering pilgrims in the region for hundreds of years. (God's Battalions by Rodney Stark lays out the history.)

Historian Thomas Madden puts it this way:

It is often assumed that the central goal of the Crusades was forced conversion of the Muslim world. Nothing could be further from the truth. From the perspective of medieval Christians, Muslims were the enemies of Christ and His Church. It was the Crusaders' task to defeat and defend against them. That was all.

That sounds pretty close to what many Americans are calling for today when it comes to ISIS.

-Slaughtering non-believers. The popes and bishops throughout the crusading periods condemned such activity, particularly in the case of the Jews.

One can't establish an equivalence between massacres that were incidental to the Crusades in the Middle Ages – a time before Geneva Conventions, surveillance drones, and federal databases, when "war is Hell" was an understatement – and massacres that are the explicit aim of ISIS in the present day. There are apples and oranges, and then there are apples and a Kalashnikov soaked in apple juice.

-Drove out and slaughtered the Jews of Spain, Portugal, etc. Shaw includes no citations or specific figures, perhaps because the claim that the Crusades or the Christianity of the time endorsed such atrocities cannot be substantiated. (Check Myth 5 here.)

A good treatment on the Catholic Church's legacy regarding Jews can be found in Rabbi David Dalin's The Myth of Hitler's Pope. "Popes regularly condemned anti-Semites who sought to incite violence against Jews," Dalin writes. He quotes Madden: "of all medieval institutions, the Church stood alone in Europe in its consistent condemnation of Jewish persecutions." And he quotes Cecil Roth, who "achieved international renown as the most prolific and widely read Jewish historian of his generation":

Of all the dynasties in Europe, the papacy not only refused to persecute the Jews ... but through the ages popes were protectors of the Jews. ... The truth is that the popes and the Catholic Church from the earliest days of the Church were never responsible for physical persecution of Jews and only Rome, among the capitals of the world, is free from having been a place of Jewish tragedy. For this we Jews must have gratitude.

One could also research Israel Zolli, the World War II-era chief rabbi of Rome, who converted to Catholicism in 1945. The Crusades must not have bothered him overmuch.

-Conquered and converted much of Africa, etc. A sore spot for any Christian who wants to defend the Crusades is the requirement to admit that they were a failure. Regarding Africa, the Crusaders held their kingdoms in the northern part of the continent for only a few generations before Muslims overwhelmed them. All the subsequent Crusades likewise failed. So there was not much conquering or converting to be found.

As for Asia and the Americas, Shaw will have to take those up with the missionaries. Perhaps Catholics are to be execrated for evangelizing as well.

-What was done in the name of Christ... It bears repeating that ISIS's campaign is called for in the Quran. Those seeking similar exhortations in the Bible, or among history's popes, will be hard-pressed to find them. Thus, when Muslims open fire in a theater or military base shouting "Allahu akbar," they follow the prescriptions of their faith. If a Catholic were to do the same (presumably sans "Allahu akbar," but this is, it is worth emphasizing, a hypothetical), he would defy the prescriptions of his faith.

It makes sense when liberals, who despise Christianity and especially the Catholic Church, peddle malicious falsehoods about both. On the other hand, why a conservative writer in a conservative publication would slander the Church in a piece taking Islam to task should be an occasion for much puzzlement.

Shaw's blog post is about 800 words long, with a mere hundred comprising anti-Catholic fulminating. Those words could easily have been edited out and replaced with a true parallel – say, to the blood-soaked legacy of the USSR, who pursued communist colonization with ISIS-like fervor and similar gruesome results. (While we're at it, we can replace the evil, evil Church hates science because Galileo myth with the far more apt reference to Soviet-enforced and utterly bogus Lysenkoism.)

Rabbi Dalin trenchantly notes in The Myth of Hitler's Pope that to demonize the Catholic Church in the fight against anti-Semitism is to travel a path of lies. Likewise when it comes to misrepresenting the Crusades to excoriate the campaign of ISIS. It's not that there is no comparison between the two; obviously, a comparison can be made. It just happens to be a terrible one.

One commentator yesterday noted that "Mr. Shaw needs to expand his reading list on the Crusades a bit." That about sums it up. Dalin's Myth and Stark's Battalions would be good places to start.

Drew Belsky is American Thinker's deputy editor.