There were many ways in which all characters, including Eliezer's father, reacted to the evils of the Nazi regime.
First, Elie says that his father was a man who did not really show emotions. However, when he saw the brutality of the Nazis, he broke down. Elie says that this was the first time he saw his father weep.
Second, throughout the memoir, Elie's father showed incredible resolve to live. He also sought to protect Elie. From this perspective, we can say that the dehumanization did not make him lose hope or break him to such a point where he forgot to be a decent human being. He always tried to love Elie and provide for him. In one touching section, Elie records an act of love toward him.
We were able to breathe again. My father had a present for me: a half ration of bread, bartered for something he had found at the depot, a piece of rubber that could be used to repair a shoe.
Even to the end, Elie's father sought to protect his son, even when he was dying.
On the third night of our journey, I woke up with a start when I felt two hands on my throat, trying to strangle me. I barely had time to call out: "Father!"
Just that one word. I was suffocating. But my father had awakened and grabbed my aggressor. Too weak to overwhelm him, he thought of calling Meir Katz:
"Come, come quickly! Someone is strangling my son!" In a few moments, I was freed. I never did find out why this stranger had wanted to strangle me.
In the end, Elie's father did not make it, but he did not let the dehumanization reduce his sense of love, loyalty and humanity.