I don’t know that I can accept that. The history of every civilization I’ve studied, from Egypt to Mongolia, is a history of war, conflict, and conquest. Even primitive tribes battled each other constantly. And a lot of that warfare was conducted up close, face to face. You looked your enemy in the eye and watched him die when you rammed a spear into his guts.
And then there was the oppression of one’s own fellow citizens, whether in the form of feudal tyranny or outright slavery. The Roman practice of decimation, the Terror of the French Revolution, the Holocaust, Attila, Genghis, the Shoguns ...
If man is not by nature murderous, it sure doesn’t seem to take much to make him so.
Therein lies the paradox. We see history, as you have posted, and conclude what you have. OTOH how do you explain things like this, of the muskets recovered on the battlefield, of fallen soldiers during the Civil War, most were loaded 5 or 6 times but never fired. The rifles of soldiers killed in the Battle of the Bulge were found to have NOT BEEN FIRED. I can give example after example of the fact that Joe Six Pack is NOT a killer. He just ain’t.