I knew there must be theology on this. From a friend in Canada:

“Mr. Derbyshire—On your question: Should states be judged by principles of individual morality? Reinhold Niebuhr is the theologian you are looking for. The obligation of the individual, Niebuhr wrote in _Moral Man and Immoral Society_, is to obey the law of love and sacrifice. ‘From the viewpoint of the author of an action, unselfishness must remain the criterion of the highest morality.’ But governments are not individuals; they are not principles but agents. They are trustees for the happiness and interest of others. Niebuhr liked to quote Hugh Cecil’s argument that unselfishness ‘is inappropriate to the action of a state. No one has the right to be unselfish with other people’s interests.’

“In short: the individual’s duty to self-sacrifice and the state’s duty of self-preservation are in conflict. This makes it impossible to measure the actions of states by a purely individualistic morality.

“Here is one from Churchill: ‘The Sermon on the Mount is the last word in Christian ethics. . . . Still, it is not on those terms that Ministers assume their responsibilities of guiding states.’”