What theme does Bruno`s father have on Bruno about making the best of a situation?

Justification of Evil Actions

Boyne embeds questions and key ideas about the nature of human interaction into the characters' conversations in order to draw the reader's attention to larger issues. For example, Father assures Bruno that the Jews on the other side of the fence are "not people at all" - this is how he justifies to himself killing them at Auschwitz (53).

Maria's description of how kind Father has been to her serves as a commentary on the mental and emotional justification for Nazi soldiers generally, who might do kind deeds and appear to be wonderful people in other parts of their lives, while simultaneously carrying out the extermination of Jews.