True friendship.

When you find a friend, you care about him or her. True friendship does not discriminate. Bruno and Shmuel are a role model to follow. Specially Bruno, whose heart was so pured that he could not understand why those people with stripped pajamas and a star on their arms were hated and why they were kept in a place they did not want to be. 

No matter how bad Jews were considered, Bruno trusted his Jewish friend and trusted his own heart. They would keep their true friendship despite the fence  that separated then.