A long string of people are against violence for any reason at all, believing that violence begets violence, or "we reap what we sow": Jesus, Gandhi, Einstein, the Buddha, Martin Luther King, Jr., and my guy John Lennon.
Others believed that the limited use of violence can be used for good ends: Caesar, Mohammed, and George Washington. Genghis Kahn and Hitler started the same way.
Garrison Keillor below articulates a belief that I've played around with, but on seeing it here, I don't think it's so hot. Further, my work as an instructor has put me face-to-face with the "friendly, straight-talking, no-nonsense people" GK refers to. And I want to not be patronizing here: these straight-talking people's notions of patriotism are simply too vague and emotional for me -- I try to avoid all visceral emotions, except for one: James Joyce's (and other great artists') feeling of the sublime.
What makes no sense at all is when the arrogant idiot expects us civilians to support his unprincipled policy as a way of "supporting our troops." The troops are not mercenaries, they are American soldiers in a long proud tradition going back to Gen. Washington's Continental Army at Valley Forge, and what gives their mission dignity and meaning is that it comes from a constitutional government in which war is not a point of personal privilege but a matter to be openly debated, opposed, protested, reported. For the troops to fall into line is a noble thing; for civilians to fall into line is shameful.
Literary criticism training has shown me that language is used to enforce artificial boundaries and instill separative thinking. Where does America start and Mexico end? Who's an American and who is not? Who's "black" and who's "white"? These things are relative, and that does not make one a "relativist".
Simply put, it's a value to accept authority at face value -- a value that I do not share. Authority is always on the side of enforcing an artificial boundary, and usually the reasons don't make sense, or at least are fashioned for the benefit of one group of people over another.
And with war and violence, the boundaries get harder and harder to enforce, and it's an ugly spectacle. The word "enemy" ceases to have much meaning, innocent people get called enemies, ex-enemies turn to allies. "Honor" and "kill" get in a weird marriage.
And that's how things work, and GK's picture of a war "openly debated" may be more rose-colored optimistic thinking that Jesus' dictum, which speaks for itself and functions as the best conclusion I may offer:
You have learned that they were told, “Eye for an eye, tooth for a tooth.” But what I tell you is this: Do not set yourself against the man who wrongs you. If someone slaps you on the right cheek, turn and offer him your left. If a man wants to sue you for your shirt, let him have your coat as well. If a man in authority makes you go one mile, go with him two. Give when you are asked to give; and do not turn your back on a man who wants to borrow.