Why was Eliezer glad that he had forgotten seeing Rabbi Eliahou's son?

During
the forced march from Buna to Birkenau, Elie sees Rabbi Eliahou while the Jews seek shelter from
the snow in an old brick factory with a collapsed roof. The rabbi was separated from his son
during the chaos of the march and he is now looking for him. He asks Elie if he has seen the
boy, but Elie indicates he has not. Just after the rabbi has left the shelter Elie remembers
that he had seen the rabbi's son attempting to distance himself from his father. Elie
says,

A terrible thought loomed up in my mind: he had
wanted to get rid of his father! He...