"Why do there have to be men like that, men who enjoy another man's dying?" (1. 1. 11)
The spy, Harrison, muses on the mystery of evil: how can someone actually enjoy inflecting suffering on someone else? To quote Bruce Springsteen's song "Nebraska": "I guess there's just a meanness in this world."
"There are many people, General, that don't give a damn for a human soul, do you know that? The strange thing is, after playing this poor fool farmer for a while I can't help but feel sorry for him. Because nobody cares." (1.1.64)
As in the previous quote, Harrison is still hung up on the heartlessness or plain indifference of many people. The war itself might feel like an excellent example of human heartlessness—despite the fact that, ultimately, according to Shaara, it's being fought to liberate slaves.
He had not thought God would do a thing like that. He went to church and asked and there was no answer. He got down on his knees and pleaded but there was no answer. He got down on his knees and pleaded but there was no answer. She kept standing in the door: the boy is dead. (2.5.4)
Longstreet's life is turned totally upside-down when three of his children die during a terrible Christmas season. He's unable to make sense of it or to understand why God would allow this kind of suffering to happen. The Killer Angels doesn't really strive to provide answers to these questions—it just dramatizes the doubts and inner conflicts.
"I don't like bayonets." He squinted at Chamberlain, shrugged foolishly, blinked and yawned. "One thing about war I just don't like. Different, you know? Not like guns and cannon. Other men feel same way. You know what I mean?" (4.1.22)
Tom Chamberlain doesn't like bayonets because stabbing someone feels so much more gruesomely intimate. You need to get close and confront the life you're trying to destroy. But isn't that what killing is? Is it any better if it's done by gun or by cannon?
"Lawrence, I been down to the hospital. Godawful mess. No shade, no room. They lying everywhere, out in the sun. They cuttin' off arms and legs right out in the open, front of everybody, like they did at Fredericksurg. God they ought to know better, they ought not do that in public. Some of them people die. Man out to have privacy at a time like that. You got to yell sometimes, you know? Lord…" (4.3.39)
Wartime suffering isn't just painful—it's undignified. These soldiers are exposed, bleeding and dying in front of everyone. There's no way to conceal it or find some privacy. It's another example of humans becoming just "animal meat."
"No," Chamberlain said. He was thinking of Kilrain: no divine spark. Animal meat: the Killer Angels. (4.6.18)
According to Kilrain, there's no God or soul. Life is more of a dog-eat-dog struggle. But by linking the idea of animal meat with the idea of killer angels, Chamberlain seems to question whether humans are destined always to be "meat." Sure, humans have tendencies toward violence, and they even have the tendency to dehumanize each other, but they have an angelic side, too. It's as if the real battle happens within each individual, between killer and angel.