Characters in Of Mice and Men vilify Crooks based of him being African American. They look down on him and don't allowing him to do certain things based on his skin colour.
I ain't wanted in the bunkhouse, and you ain't wanted in my room."
Curley has a lot of aggression which stemmed from his life as a boxer but he often jumps to conclusions and lashes out at people and things when something doesn't go his way.
Come on, ya big bastard. Get up on your feet. No big son-of-a-bitch is gonna laugh at me. I'll show ya who's yella."