Describe George's reaction when Slim calls Lennie a "cuckoo".

From the text:

"He ain't no cuckoo," said George. "He's dumb as hell, but he ain't crazy. An' I ain't so bright neither, or I wouldn't be buckin' barley for my fifty and found. If I was bright, if I was even a little bit smart, I'd have my own little place, an' I'd be bringin' in my own crops, 'stead of doin' all the work and not getting what comes up outa the ground."