Like the others on the ranch, Crooks and Curley's wife are alienated from the others, a condition which produces an animosity and meanness born of fear. With these two characters, their fears are, perhaps, enlargened by their singular positions; Curley's wife is the only female on the ranch, and Crooks is the only black.
Ironically, it is often the lowliest who are cruelest when provided the opportunity. Just as the Ewells of To Kill a Mockingbird charge Tom Robinson, a black, with criminality when he has done no wrong, so does Curley's wife, the greatest misfit of all on the ranch, deprecate with vituperation the "negro stable buck." For, imbued with a new confidence after the white men have included him in their conversations, Crooks tries to remove her from his area,
"You got not rights comin' in a colored man's room. You got no rights messing around in here at all. Now you jus' get out, an' get out quick. If you don't , I'm gonna ast the boss not to ever let you come in the barn no more."
Enraged that Crooks has far overstepped his social bounds, Curley's wife who has the advantage of being white and in a higher social position, turns her wrath and scorn upon him:
"Listen, N---,...you know what I can do to you if you open your trap?" [Implying she can get him hanged]
Suddenly reduced again to the lowest stratum of society, Crooks backs up against the wall and says subserviently, "Yes, ma'am."
This exchange between Crooks and Curley's wife demonstrates the inherent cruelty of the human being, who, even as he writhes in his own misery, will yet vituperate against others if afforded the opportunity. For the author, John Steinbeck, these two characters underscore his theme of alienation and the theme of man vs. man.