There is nothing that yanks the chain of a true religious fanatic more than a heretic. A heretic is 1000x as offensive as a simple nonbeliever. This has always been true. It was the entire basis of the thirty years war, and has been true in Islam since Muhammed died. Hell, supposedly "peace loving" sects of Budhists monds throw down in the streets with other sects of monks over doctrinal supremacy. Your thesis that the truely faithful wouldn't fight among themselves is directly contradicted by the entire history of every religion that has ever been.
But I also think we should not completely dismiss the efficacy of ideology in the creation of atrocities. If the German people or the American people would not have been consumed with a feeling of racial superiority, would they have been able to commit the atrocities and genocides they each committed? So, I personally think that ideologies with certain aspects (racism, eschatological goals, divine right, etc.) imbue the populations and leaders who buy into such ideas with a greater likelihood to commit atrocities. Now, personally, I think Christianity is just as bad as Islam.
That's not what I said... I said it's hard to point to religion when people of the same faith are fighting each other. I never said they never wouldn't fight each other. But it seems more about politics when they do and not religion. The thirty years war involved two different religions and turned strictly political half way through it. We live in a Christian nation that let murderous Christian hate groups like the KKK exist... There's no difference.
