Bruno's father in The Boy in the Striped Pajamas was loyal to Hitler and the Nazi regime. This is evident based on several examples throughout the book.
The first and most obvious example of Bruno's father's loyalty to Hitler was his acceptance of the position of commandant at the death camp Auschwitz. Hitler needed loyal servants who would ignore the humanity of Jewish people and follow his bidding to kill innocent people. In the novel Bruno's father is extremely proud of his promotion and so was Bruno's grandfather (this may be an example of how the majority of the family was loyal to Hitler).
The second example that proves Bruno's Father was loyal to Hitler was that he hosted him for dinner which led to his acceptance of commandant. While working in Berlin, Bruno's father came home one night in “a state of great excitement”. Hitler had invited himself to dinner. The fact that Bruno's father was excited shows his reverence for Hitler. Although Bruno's mother and grandmother objected to the promotion because they were fearful of the impact on the children, Bruno's father takes the job anyway. This loyalty to Hitler eventually does put Bruno in danger and unfortunately leads to his demise.