In Of Mice and Men, the author, John Steinbeck, criticizes society by what happens to the characters in his story.
Look at the character of Lennie Small. You could think of him as representing the weakest (even though he is physically strong) and most vulnerable people in society. However, he would be helpless without George by his side to guide him.
But even with George, society still beats Lennie down. He is literally beaten by the jealous Curley, and then hunted like an animal when he accidentally kills Curley’s wife. In Steinbeck’s view, it is not possible for society to take Lennie’s innocent intentions into account. People like Curley (who leads the hunt for Lennie) will always prey on the innocent. Society can cruel and unforgiving.