How does Crooks upset Lennie?

Crooks teases Lennie about his lack of self-reliance; he tauntingly asks Lennie what he would do if George were injured. Unable to think hypothetically, Lennie thinks that George is actually under threat. With some difficulty, Crooks calms Lennie down and takes on a kindlier demeanor. His sour attitude remains, however, as he tells Lennie that his dreams of owning a farm with rabbits is unlikely to amount to anything tangible.