Why doesnt Kaleb Wallace attack Morrison when they meet on the road?

The children go with Mr. Morrison in the wagon to lend Papa's planter to Mr. Wiggins at his farm, six miles away. On the way back, Kaleb Wallace's pickup truck stops in the middle of the road, blocking their path. Kaleb threatens to gun down Mr. Morrison for hurting his brothers. Mr. Morrison calmly looks in the pickup to see if Kaleb is carrying a gun, then uses his enormous strength to move the pickup to the side of the road. As they drive away, Kaleb yells that he is going to "get" Mr. Morrison.