Why did Rat Kiley torture and kill the baby buffalo?

Another “true” story that O’Brien tells is that of a water buffalo. The day that Curt Lemon died, the company found a baby water buffalo in the woods. Rat Kiley tortured it. He shot it in all the places in its body where a wound would not be fatal. Kiley had just lost his best friend, O’Brien explains, to help justify the story. He tortured the buffalo and cried. Riley was taking his anger out on the water buffalo. He inflicted all the torture and pain he wanted to inflict on the Vietnameses on an innocent animal. He cried because he was wrong, because he couldn't bring back his friend or the innocence they'd all lost. Back home, when old women cry listening to that story, O’Brien says they don’t understand. They understand that war is about beauty and friendship, too. They only understand tired generalizations: “war is hell", etc.