As we look at history, the dropping of the bomb on Hiroshima remains justified, as the massive death was still paltry compared to the amount of death that would have been caused by a protracted invasion of Japan. Sometimes violence is supported by bean counting. Doesn't mean we will rest easy with the thought, and it doesn't mean the afterlife will be any kinder to us for making those kinds of decisions, but this is perhaps the ultimate example that answers the question.