Lennie smiled with this bruised mouth. "I didn't want no trouble," he said. He walked toward the door, but just before he came to it, he turned back. "George?"
"What you want?"
"I can still tend the rabbits, George?"
"Sure. You ain't done nothing wrong."
"I di'n't mean no harm, George." (3.268-272)
Um, okay. Lennie may have meant no harm, but he still has a tendency to kill the animals in his care. So, maybe "doing no harm" isn't the best criteria for putting a man in charge of a warren full of rabbits.