Roll of Thunder/hear my cry-Mr. Jamison says that killing a black man is a minor consideration. why?

According to Mr. Jamison, a white man killing a black man is of no consideration because punishing a white man would denote equality.

"That they should be punished just as if they had killed a white man, and punishment of a white man for a wrong done to a black man would denote equality. Now that is what Harlan Granger absolutely will not permit.”