There is a widespread myth about religion and war. The biggest sources of war throughout the 20th Century were the nationalist ideologies of Germany and Japan, and the completely atheistic ideology of the Soviet bloc. Mao, Stalin, and Pol Pot have more blood on their hands than a thousand Torquemadas.
If you think God isn't the answer, then there is nothing stopping you from concluding that something else is the answer, and that answer (whatever it is) is something you DO want to kill or die for. If you think God IS the answer, then you may conclude, as many have, that force is a lousy way to promote that answer, because religious commitment by definition needs to be voluntary, and cannot be forced. But you can also become a Grand Inquisitor or a terrorist. If you are a secularist, you can believe that goals of humanity must be achieved by violent revolution, or you can trust democratic social institutions to achieve those goals peacefully.
The rise of Islamic terror has skewed our historical perspective quite a bit, as I see it.