You gotta be kidding. You must be born yesterday.
Historically, Christians have killed more people in the world and started more wars than those belonging to any other religion. Stalin alone killed 15 million. Not to mention the Inquisition, wave after wave of genocide during European expansionism and colonization in the past 600 years, endless wars including the 2 world wars, the Crusades, witch trials, violent missionary expeditions, etc.
Just so, the twentieth century has seen more wars than the previous ten centuries combined, most of them started and abetted by Christian nations.
The reason why you see relative peace in Western nations today is that they've learnt their lesson after 2 millennia of warring, and are now secular states, no longer Christian. They have separated Church from state.
The Abrahamic religions – Christianity, Islam, Judaism – have caused more bloodshed than the rest of the world combined. These religions of the Book are innately intolerant, exclusionary, and believe in the Sword to spread the word of their God.