What is the story about the Berrys? Why does Papa warn the children about going to the Wallace store?

T.J. tells Stacey that Mr. Berry and his two nephews were burned by some white men the previous night. Papa tells the children that Mama has heard about other older kids going to the store to dance, buy bootleg liquor, and smoke. He says he does not want his children going there and says he'll "wear [them] out" if they go there.