"WW2 cost 60 million lives, but if the world had lain down its arms and opened its borders to Hitler's armies, the world would be a worse place."

Hitler was not an issue in 1914. And had the 1914 war not been fought the conditions which led to the rise of both Hitler and Stalin would not have arisen, as Jim has pointed out. And possibly Spanish flu into the bargain. So we might now be laying more than 100 million deaths at the door of our refusal to negotiate peace in 1914, and again in 1916.