Grandma tells Janie that the "de nigger woman is de mule uh de world"?. Do you think that Logan Killicks was starting to treat Janie like a "mule" when she left him?

He was. He expected Janie to work like a mule and be obedient like one. Ironically life is just as bad with Jody Starks. The whole mule episode, Matt Bonner about his skinny yellow mule, was a metaphor for what Janie's grandmother was talking about.