It's not that war is good, it is bad, and that's exactly why it exists and will continue to exist. It's not used to reward, it's used to punish opposition for some political, social or economic goal.
Many peaceniks and anti-war types think that war is a human trait; it is not, we just have the most extravagant and complicated wars. Almost all animals on the planet engage in war as a means to compete as part of evolution. An example would be neighboring ant colonies. Their proximity to each other is all that is needed for the two colonies to engage in a war.
