What did Kiowa try to tell O'Brien later?

Kiowa told him he did the right thing, that the man would have died anyway.

Later, I remember, Kiowa tried to tell me that the man would've died anyway. He told me that it was a good kill, that I was a soldier and this was a war, that I should shape up and stop staring and ask myself what the dead man would' ve done if things were reversed.