Right on cue, the right wing is in high dudgeon over comments President Barack Obama made during last week’s National Prayer Breakfast that are supposedly anti-Christian and offensive.

The president was pointing out that the terror and bloodshed of groups like ISIS is hardly unique from an historical perspective.

Here is what the president said that has the Religious Right and its Tea Party sidekicks so worked up: “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. In our home country, slavery and Jim Crow all too often was justified in the name of Christ.”

You would have to be a complete ignoramus who has never picked up a history book not to know that this is true.

Let’s consider just the Crusades for a moment. Depending on which historian you listen to, there were seven or eight major crusades between 1096 and 1291. They were exceedingly violent events.

How many people died? It’s impossible to say given the record-keeping of the time, but many historians say 1 million is a low estimate. Jay Michaelson of Religion News Service put the figure at 1.7 million in a recent column. Far-right Catholic apologists for the Crusades – yes, there are such people – peddle much lower figures, but these aren’t taken seriously.

None of this is exactly a secret. There are many good histories of the Crusades. I recommend The Dream and the Tomb: A History of the Crusades by Robert Payne. For anyone foolish enough to believe that the Crusades weren’t so bad, here are some things to consider:

* The First Crusade was led by a ragged poor man named Peter the Hermit. Peter’s army consisted mainly of ordinary folk, among them women and children, armed with primitive weapons. As they marched across Europe, Peter lost control of his army, and the first battle it fought was against other Christians. A square-off in Hungary resulted in about 4,000 deaths and an ensuring clash that Payne calls “a massacre.” Near Belgrade, residents saw Peter’s army approaching and fled. The crusaders set fire to the city.

* Peter’s patchwork army was no match for professional Muslim warriors. Most were slaughtered in battle. Princes and kings took up the crusade with better-equipped forces. One army, under Prince Bohemond, encircled the city of Antioch. After capturing a band of spies, Bohemond had them cooked alive on spits as a warning to other spies.

* Not all Crusades were against Muslims. During what is known as the “Albigensian Crusade” in 1209, Pope Innocent III ordered Crusader armies to wipe out followers of a Christian heresy known as Catharism. Beziers, a Cathar stronghold in France, was besieged. The city’s defenses were breached during a sortie, and the invading army forced its way in. An estimated 15,000-20,000 people were killed. Ironically, many who were killed were undoubtedly not Cathars. Some years later, a story circulated (possibly apocryphal) that an abbot had been asked by soldiers how to differentiate between heretics and non-heretics. The cleric allegedly replied, “Kill them all, God will know His own.”

* Late in 1218, during the Fifth Crusade, the Crusaders attacked the city of Damietta in Egypt. A long siege dragged on for nearly a year, and, as Payne writes, “famine and pestilence stalked the city.” When the Crusader army finally broke through the city’s walls, they found mostly corpses. An estimated 80,000 people had died. About 3,000 were left. Most of them were sold to slave markets.

These are just a few stories. There are many like them. You need a strong stomach to read about the Crusades.

To bring up this history in no way excuses the barbaric acts of groups like ISIS. Rather, some historical context helps us understand that zealots fueled by dogmatic beliefs are capable of great evil. The vile acts of ISIS are so shocking in part because they are spread via modern technology. But they aren’t new. We’ve seen this kind of violence before – from many religious groups.

Maybe, just maybe, Obama wasn’t trying to knock Christianity. Perhaps he was merely pointing out something that anyone who has ever picked up a history book knows to be true: that in this world, violence in the name of faith has a long and unfortunate pedigree.