The catcher in the rye Mario Melendez

At the end of chapter 18 when Holden saw that movie about war he thinks that he wouldnt want to go to war. But then he goes on to say if he was in the army he would want to just die, or sit on top of an atom bomb. But then in chapter 21 of the book when he goes to talk to his sister she tells him that their dad will kill him if he finds out he got kicked out of school. But he insistes that he wouldnt kill him. i guess i dont understand, why would Holden insist that his dad isnt going to kill him but then he is so willing to die when he talked about being in the army. It seems to me that a theme in this novel is death so it doesnt make sense he would feel so strongly about his dad not killing him.

Works cited:
Salinger, J.D. The Catcher in the Rye. Little, Brown, 1951. Print.