Humans, as a whole, are not particularly blood thirsty, homicidal monsters. They have to be made to perceive that the "other side" is composed of bad people whose intentions and policies will harm them . By the late 1850's both Northern and Southern leaders and media were doing a very good job of presenting to each side a vision of their opponents as really bad, dangerous enemies out to "get you", the filthy, greasy mechanics image and the Uncle Tom's Cabin scenario. A couple generations before that the Sons of Liberty did an equally good job of persuading American colonists to see the British people, the monarch and the Redcoats, as inimical to Colonial interests and that was before the war broke out and George III was blamed for every calamity to hit the Colonies in the 18th Century short of plague. I am certain the British press did the same thing presenting American demands as the product of ungrateful, spoiled brats who needed to be chastised for their obtuseness. Fanning the flames of hatred is a necessary element in getting people to kill each other and there has never been any shortage of people willing to do that.
One of the reasons for the widespread fraternizing between Northern and Southern soldiers in the war was that when interfacing with their enemies they discovered Billy Yank from Indiana was not all that different from Johnny Reb from Tennessee. Despite all the stories about the beastly Hessians in the Revolutionary War, they turned out not to be such monsters when they fell into American hands at Trenton and Saratoga. They in turn were startled to discover that Americans were not killing the wounded,mutilating their dead and eating them for breakfast. The Christmas Truce of 1914 was frightening to both the Allied and Central Powers' high commands because, as the soldiers intermingled with their opponents, they again discovered they were not the caricatured monsters they had been persuaded they were. I swear that if the media and government were given free rein to do it, they could convince the entire populace to enlist in the army of Lucifer by making the angels of light look bad.
I am not naïve about this. There really are bad people who come to power and then try to do evil things to us and our neighbors and they must be resisted by force of arms, but I feel that just as Wall Street has accurately forecast ten of the last three recessions, that in our history, both American and Western History, governments and media have created enemies where they did not really exist, propelling us into wars, unnecessary wars, for goals and ends not worth the cost in blood to those who must fight them. Yes, people can be bamboozled and goaded into killing each other, but to pull that off requires unscrupulous, conscienceless demagogues fanning the flames of hatred and, as I stated above, there has never been a lack of such individuals.