Religious intolerance is a part of history, and our world today, we all know that. If there never were monotheistic religions, I'm sure murderous fanaticism would have taken another form. It already has. It's name was Communist totalitarianism and Nazism. The millions murdered in Nazi occupied countries, Stalinist Russia, and Maoist China, not to mention Cambodia under the Khmer Rouge were not killed by those purporting to practice monotheistic religions. It could be argued, though, that the same sort of fanatical mindset is at play in those who do murder innocents in the name of their twisted versions of religion, as it is in those who murder on non-religious or anti-religious beliefs and ideologies.

let's not forget that Christianity also spawned a significant part of pacifism and nonviolent action. Gandhi cited Jesus's teachings as a major influence, and we know that ML King, Jr. and many other significant activists in the civil rights movement (not all, I know) cite their belief in Christian nonviolence, and their training in, for example, Rev. Jim Lawson's workshops in how to apply Christian nonviolence to practical purposes.
Religion has always brought out some of the best AND the worst in humanity, depending on how one interprets or misinterprets it, and depending on how it is part and parcel of politics, and of people who are desperate psycopaths who murder in its name.

Chanteyranger