What a COP out. Your argument is full of holes. Religion is not the reason why people kill each other. However religion may be used as a tool by some to destroy others.
There are plenty of world dictators and evil men I.E. Stalin, Pol Pot, and Hitler who had no need for Christianity or Islam. People will find plenty ways to kill one another. Sure religion may be used as an excuse, but I can think of alot of excuses that humans use to kill one another. I.E. race, class, economics, technology.