Whose Side is He On?

Why is it that religions of peace have followers that exibit so much violence? This has gone on since the beginning of time. I won't go into history today in order to keep things current. The President of the United States appeared on TV and said that God was a deciding factor in his decision to go to war(this is not word for word). Muslim leaders have stated that Allah is behind them and that he will help them fight and kill the western nations. God and Allah. One and the same. Where and when did He give man the right to fight and kill each other? The Arabs fight against the western world in the name of Allah(God) and the Western world is currently fighting muslims in the name of God(Allah). Which side is God/Allah on? Could it be that the devil has tricked both the westerners and the muslims?