How the hell else are you going to get people to kill for you? You: "Hay brah, war is bad, now go invade that country." Soldier: lolno You: "Hay ppl, war is bad, now support my invasion." People: lolno Great job. To be clear, there are good reasons to fight a war. But, more often than not, those reasons don't come into play when you need to go blow some shit up. Nobody wants to hear that you're pursuing military intervention to secure your financial interests in Latin America or something. While it might be the most effective way of making sure your corporations have a monopoly over the resources and labor in that area, thus providing your people with the lowest-cost products, it clashes with the people's idealistic vision of Life Should Be. So you have to pretend reality is just like what's in their heads.