Why doesn't Janie like to talk about her mule story?

There is a strong parallel between the mule and Janie. Recall that Nanny warns Janie in the first chapter that the "nigger woman is de mule uh de world." Janie is the first person to be angered by the porchsitters' baiting of the mule; she identifies with the mule's struggle. Although it seems as though Joe cares for the mule because he pays five dollars to protect it, it becomes clear that he is only exploiting the mule for further self-aggrandizement. He literally uses its carcass as a platform for the "great eulogy" that he performs. Joe prevents Janie from attending the funeral, so no one is there to speak out against the mule's desecration.