Whenever a religious fringe group rises up in arms, be it Al-Qaeda, ISIS, Christian murderers of abortion providers, or whatever, pundits amass to fight at the steps of the podium to be first to proclaim that what those people do is not motivated by religion, that "real religion" is not like that. This is bizarre, and either dishonest or foolish.
Let's be clear: I don't like Islam, but there are about a billion and a half Muslims out there who aren't terrorists, the vast majority of whom would (I presume) be no more eager to decapitate people than I would. I am not suggesting that, for instance, ISIS aren't a fringe group. Of course they are. (And of course there are lots of non-Muslim Arabs, and the large majority of Muslims aren't Arabs to begin with.) Nor do I think that Islam is inherently more vicious than Christianity, though the latter has been somewhat defanged by the Enlightenment.
That said, it's very odd that these commentators always insist that any evil whatsoever cannot be motivated by religion, as "properly" understood. It's always other factors -- political, historical, cultural. Of course, all that context is always significant, and sometimes religious divisions are secondary (IRA?), but claiming that it's about history and culture instead of religion is an implicit assertion that religion has no influence on culture and history. If someone says that people are never motivated to evil by religion, they're implying that people's beliefs do not influence their behaviour; or perhaps that religious beliefs aren't important enough to be acted upon.
Well, that's what they would be implying, at any rate, were they not busily committing logical fallacies to protect, pardon me, the sacred cow of religion. If someone does something nice and credits “do unto others” or “whatsoever you do unto the least of my brothers”, if Muslims give to charity and say it's because the Quran tells them to, everyone is happy to accept their stated motivation. But the moment they do something bad, it is widely denied that their motivation could possibly be what they say it is, even if they can cite verses in their support. “No religion condones the killing of innocents,” said Obama, apparently unfamiliar with Psalm 137-9, Hosea 13:16, and other pleasant tidbits.
I don't believe in any of this. I believe that when someone claims to act out of religious conviction, the possibility should be entertained that they may be telling the truth, whether the act be good or evil; moreover, that even if an interpretation is a minority view, that doesn't disqualify it from being religious. I believe that many people take their religion seriously and do act on their beliefs, sometimes to great good and sometimes to great evil. Let me repeat that: Religion in general, and certainly the big monotheistic ones, can motivate people just as easily to good and evil. That, precisely, is the problem—not that people of any religion are somehow intrinsically evil, but that people mistake scriptures for moral compasses.