Joe's basic desire to reject everything from women is revealed in his relationship with Joanna. That is, even though Joanna leaves him food, he still prefers to steal it. And even though he had already seduced her, he prefers to violate her anew each time. With these acts, Joe is asserting his masculinity. He is refusing to allow the woman to have any influence on his life. And each time he sleeps with Joanna, it is "as if he struggled physically with another man."
The reader should compare Joe's reaction to the food that Mrs. McEachern brought him to his reaction to the food left for him by Joanna. In both cases, he violently hurls the food away.
Joanna Burden's story of her ancestors places her in a position to help Joe. She has inherited the burden of the Negro race. Her willingness to accept a person at his own value should have prepared Joanna to accept Joe, and throughout this chapter, it appears that Joanna is accepting Joe for what he is.
At the end of the chapter, Joe says he doesn't know his parents but that one was part Negro. When Joanna inquires how Joe knows that he is part Negro, he tells her that he doesn't definitely know, but he has always assumed that he has Negro blood. The point is that Christmas feels himself to be a Negro, and he has lived his life with this assumption. His problem, then, involves his belief that he possesses two bloods, and therefore, his attempts to reconcile these two bloods or to find acceptance for both are crucial to his life.