First, he is defending his way of life. Your cattle drive is blocked by barbed wire. Your newly planted wheat is being trampled by cattle. Your newest troopers do not understand how important it is to do things By the Book. Your deputy was shot by a drunken cattleman.
Reason creates abstract ideas, some of which men are willing to die for.
Looking at any given culture's past, one can see how such concepts can help a culture grow and thrive. This is Good. One can also see how these concepts mix explosively with the status drive of the peer bond, the territorial drive, and the instinctive readiness to see a rival peer group as The Enemy. This can be seen as Evil. If men contested rationally for resources, compromise would be easy, there would be few conflicts, and the scenario would be boring.