Lying to protect

During their brief stay at Auschwitz, Eliezer and his father run into a distant relative from Antwerp. When the man inquires about his family, Eliezer's father lies and says that everyone is alive and well. Later, Eliezer lies to Rabbi Eliahou about his son. Is lying the best choice in these situations or should Eliezer and his father have been truthful? Is lying acceptable to protect someone's feelings?