The ummah that was never there

[kılıç_mehmet]

Christians did not slaughter each other because of religion.

Sure they did. And they took time out to slaughter jews and muslims when the opportunity presented itself.

"God" told them it was okay, you know?

No, I don't know. Can you tell me for sure that the hundred years war between England and France was due to a religious conflict?
Or can you tell me for sure that the slaughter of jews or christians was a religious matter?
Jews have been persecuted ever since they had contact with other nations. Their own holy books describe how the Egyptians, Assyrians, Romans and many other pagan nations had been at odds with them.
And the Buddhist Mongol Kublai Khan and his Christian Turkish Queen Dokhuz Khatun have been responsible for the sack of Baghdat, and the death of the Caliph who was left to starve in his own treasury.