This early incident in "Of Mice and Men" is used by John Steinbeck as an illustration of the alienation of the men in this Depression era novel. Distrust is the quality of the modern world in which people live in alienation from one another.
As a socialist himself, a key theme of Steinbeck's is the need for brotherhood in society. As George and Lennie have each other, they fare better than the others. George affirms their fraternity:
Guys like us, that work on ranches are the loneliest guys in the world. They got no family. They don't belong no place...With us it ain't like that. We got a future. We got somebody to talk to that gives a damn. We don't have to sit in no bar room blowin' in our jack jus' because we got no place else to go.