George is intolerant of Lennie because Lennie refuses to give him the mouse. Lennie wants to walk around with the dead mouse and pet it but George has no tolerence for that.
"'Give it here!'"
"'It's on'y a mouse, George'"
The boss became intolerant of George because he wouldn't let Lennie talk for himself, he thought that he was trying to pull something over on him.
"'He can do anything. Just give him a try.'"
"'Then why don't you let him answer? What you trying to put over?'"
Carlson was intolerant of the smell coming from Candy's dog. That is why he decided that they should kill it. Candy didn't want to, but Carlson just had no tolerance for it anymore that he convinced him.
"'God Awmighty, that dog stinks...I can't stand him in here...Why'n't you shoot him, Candy?'"
In chapter 4, Intolerance is a big theme. As soon as Curley's wife came into the barn, it was clear that everyone in there was intolerant of her being there. Candy, Crooks, and Lennie had intolerance for the behavior of Curley's wife.
"'You ain't wanted here. We told you you ain't.'"
Curley was completely intolerant and angry about Lennie killing his wife. Slim tried to calm him down and make him stay but he was super mad.
"'I'm gonna shoot that big bastard myself, even if I only got one hand'"
"You'd better stay with your wife, Curley"
Lennie is having hallucinations from being so afraid and alone. He is intolerant of them because they are telling him that he would not be able to live out his dream and tend rabbits with George.
George won't do nothin' like that... He's nice to me.
"'If you think George gonna let you tend rabbits, you're even crazier'n usual. He ain't. '"