O'Brien doesn't exactly say that war stories are not moral--he says that you can tell a true war story because it does not teach a lesson, or have a point. It is why he plays throughout the book with stories, and the truth. To make a point, he sometimes takes an internal struggle, and gives it an external setting. For example, his tale of how he came to the decision to go to Vietnam may have been as simple as O'Brien sitting at his kitchen table and weighing the pros and cons. But turning it into a story of traveling to the Rainy River makes it, in some way, more true than what may "really" have happened. With Lemon's death, he is again telling what it must have been "really" like. Is it the "truth"? What do you think?
In The Things They Carried, O'Brien gives the recipe for "How to Tell a True War Story" by saying the stomach should believe it. It must pack an emotional wallup. If it doesn't, it comes across as manufactured, invented, moralistic, political. It becomes a lie by becoming something else--an abstraction, a polemic, a sermon--not a story. A war story is a love story. It brings back loving memories. It resurrects friendly ghosts.
O'Brien's thesis for the book is:
I want you to feel what I felt. I want you to know why story-truth is truer sometimes than happening-truth (O'Brien 179).
So, O'Brien says that true war stories need to be light on facts (logos) and morality (ethos). Instead, they must be visceral and brutal and gory and full of cussing (pathos). That's the way soldiers talk. That's their style. And it's been this way since Trojan war mythology.
First of all, war is absurd. It does not operate according to ethical, moral, or religious rules. Bullets are indiscriminate. During war, a soldier or storyteller does not have time to moralize. Morality and war don't mix.
Remember woman at the reading? She wanted a moral or a lesson or some kind of redeeming meaning by the end of the story he read. She didn't understand that the story itself is the lesson. She didn't understand that it was a love story.
A good story doesn't preach: it's morals are implicit, if there are any at all. To the “dumb cooze” audience reading O'Brien's novel for realistic depictions of war and conventional storytelling his thesis is a betrayal, not a paradox; O'Brien, to these readers, comes across as weak, dishonest, one so full of regret that he rejects the traditionally masculine-defined rules of engagement in both war (“kill or be killed”) and storytelling (unreliable narrator).
Lemon's death becomes a funny and beautiful thing. He reconstructs the memory by draining the focus on death from it. He drains the horror from it. If a soldier and storyteller can do that, then he can open up new perspectives that are, ironically, both beautiful and funny.