The original question had to be edited down. I would suggest that one way in which the boy shows discrimination as dehumanization is through Bruno's presence. The entire world around him as little problem with the purpose of "Out- With" and the rules of "The Fury." People like Bruno's father and Lieutenant Kotler are immune to what they do. They do not question it and eagerly comply with what is asked out of them. It is here in which discrimination is not viewed as something wrong or something immoral. Rather, it is simply common practice. It is this type of conformity that reflects how discrimination is dehumanizing. The belief that Jewish people were not human is emphasized through the common and conformist practice of discrimination against them. In order to effectively do this, people like Kotler and Bruno's father could not see them as people. Rather, Jewish people were seen as objects or "things" that need to be eliminated. Through this, discrimination is shown to be dehumanizing.
I would also suggest that Bruno's own questioning nature and his honorable upholding of friendship is so out of the norm that it, in itself, shows discrimination as dehumanizing. Bruno's friendship with Shmuel as well as his entire questioning of the social practices under Nazi rule help to bring out how discrimination is dehumanizing. Bruno's actions help to illuminate this condition, bringing attention to it because others do not do so. It is in this way where Boyne again shows how discrimination is dehumanizing.