I would say it's The Big Country. It's an old movie (1958) but it's got a great cast and a great message. It's an 'anti-Western', in which a mild-mannered guy from the East Coast (Gregory Peck) travels west to marry his fiancee, and he finds himself in the middle of a ranch war between her family and a neighbouring ranch. It's an anti-Western because it attacks the senselessness of resolving disputes with the gun. Peck's character sticks to his priinciples despite opposition from all around him, including his fiancee, and ultimately proves himself tougher than any rough tough cowboy or gunslinger.
(In the next few weeks I hope to write a hub about The Big Country).