why doesn't Elie lash out at the guard who hit his father? Why does his father claim that he's not in pain

As Elie watches his father receiving a terrible beating, he finds himself feeling numb, almost a sense of ambivalence. Elie feels drained of emotion. He can barely survive himself and looking after his father, a weak old man, is overwhelming. Elie even feels anger at his father for being weak and not smart enough to avoid Idek's wrath. I think father claims he is not in pain because he doesn't want to be a burden to Elie.