Consider the history of religious warfare....

One of the greatest religious wars, the Crusaders, extended over a period of 200 years....
Sometimes the Crusaders were successful, killing, pillaging and taking captive Muhammadan people; sometimes the Mussulmans were victorious, inflicting bloodshed and ruin in turn upon the invaders.
So they continued for two centuries, alternately fighting with fury and relaxing with weakness until the European religionists withdrew from the East, leaving ashes of desolation behind them and finding their own nations in a condition of turbulence and upheaval....

Yet this was only one of the "Holy wars." Religious wars have been many.

Nine hundred thousand martyrs of the Protestant cause was the record of conflict and difference between that sect of Christians and the Catholics....

How many languished in prisons! How merciless the treatment of captives! All in the name of religion! The Christians and Muhammadans considered the Jews as satanic and the enemies of God.