AT A rough estimate, nearly 100m Americans went to a Christian church today. And to judge by the blogosphere, many of them were feeling disturbed by something their president said this week. In the course of denouncing the villainies of Islamic State, he suggested that all religions, including Christianity, were open to exploitation by people bent on stirring up hatred, aggression or cruelty. To be precise, Barack Obama told a National Prayer Breakfast:

Lest we get on our high horse and think this [violence in the name of religion] 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...Michelle and I returned from India, an incredible, beautiful country, full of magnificent diversity, but a place where, in past years, religious faiths of all types have on occasion been targeted by other peoples of faith...acts of intolerance that would have shocked Gandhi.

Among the many ripostes, it has variously been counter-argued that i) the Crusades weren't all that bad, that ii) the Crusades were defensive wars, launched because Muslims had taken the Christian holy places and that iii) the Crusades and the Inquisition (and even American slavery) happened long ago, whereas the infamies of Islamic State are being perpetrated here and now. Among the more intelligent points is that Christianity also served as an incentive to abolish slavery and segregation.

Whether or not they are valid, all these arguments would be relevant in a college debate over which faith, Christianity or Islam, was the more benign, either in terms of its teaching or its historical record. But Mr Obama wasn't plunging into a debate of that kind. It would be strange if a serving American head of state, presiding over a country that rigorously separates religion and governance, did plunge into such a debate. That is strictly not his business.

He was making a much narrower point: that no religion has ever been immune from exploitation for nefarious ends, and that to believe otherwise is dangerous. To put it another way, people who identify with a religious organisation, even one that preaches charity and self-sacrifice, shouldn't fall into the trap of thinking that this allegiance makes them, or their co-religionists, better than other people, or less prone to commit terrible wrongs.

And they easily can fall into that trap. Here are a couple of examples. In 1969, an American officer called William Calley was put on trial for massacring civilians in South Vietnam. There was a torrent of fury from churches in the American South, which said the allegations must be untrue, or part of an anti-American smear campaign; or that if Calley had killed people, there must have been some good reason. One Southern pastor compared Calley to Jesus Christ. The logic went something like this: America is a virtuous, Christian nation, fighting a righteous war, so its soldiers must be acting virtuously.

Much more recently, there was a similar reaction in Serbia when most of the world became convinced that Serb soldiers and paramilitaries had committed terrible atrocities in Croatia, Bosnia and Kosovo, including the biggest single massacre of non-combatants in Europe since 1945. The accusations simply could not be true, because Serbs were a heavenly people with a unique devotion to their Christian heritage. Anyone who makes such accusations must be acting out of anti-Christian spite or some similarly base motive: that, strange as it might sound to outsiders, was a common reaction.

To put the point simply, if you think your side is too virtuous to sin, it probably will sin, terribly. That's why, as Mr Obama put it, "getting on our high horse" is to be avoided. Whatever you think of the relative merits of the great world religions, that argument still holds good.