What motivates Crooks to confront Curley's wife and tell her to leave his room ?

Curley's wife starts talking to Lennie, leading him on.

"Who’s George?" she asked. "The little guy you come with?"

Lennie smiled happily. "That’s him," he said. "That’s the guy, an’ he’s gonna let me tend the rabbits."

"Well, if that’s all you want, I might get a couple rabbits myself."

Crooks stood up from his bunk and faced her. "I had enough," he said coldly. "You got no 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."