why does Mr. Benett get mad in roll of thunder

The owner of the Mercantile in Strawberry cheats his black customer, Sam Tatum, and when Tatum accuses him of lying, "night men" tar and feather Tatum. When TJ tries to buy goods for his mother at the store, Barnett stops serving him and ignores him for an hour while waiting on white customers. When Cassie politely tries to remind him that they are waiting, he calls her a "little nigger," and throws her out of his store. When the Simms brothers and TJ break into his store, he comes down to investigate and RW hits him over the head with the flat part of an axe. He dies the next morning.