I'm not endorsing everything he says here.
It seems very flawed to say that war is a force for good because of the scientific and medical advancements that happened during war. Those advancements would have happened anyway, perhaps more slowly, but maybe more quickly because we wouldn't be spending most of our wealth trying to destroy each other. Nobody thinks that we should go to war to advance science. What creates innovation is a free market.
World War 1 is responsible for the spread of the Spanish Flu that killed at least 50 million people.
Sometimes war is necessary to stop aggression.