Violence never solves anything?

Heinlein has a bit to say through one of his characters in Starship Troopers about the morality of pacifism:

Anyone who clings to the historically untrue—and thoroughly immoral—doctrine that "violence never solves anything" I would advise to conjure up the ghosts of Napoleon Bonaparte and of the Duke of Wellington and let them debate it. The ghost of Hitler could referee, and the jury might well be the Dodo, the Great Auk, and the Passenger Pigeon. Violence, naked force, has settled more issues in history than has any other factor, and the contrary opinion is wishful thinking at its worst. Breeds that forget this basic truth have always paid for it with their lives and freedoms.

Though I don't exactly think of Robert "What's wrong with incest again?" Heinlein as an authority on morality.