The motif of racism
Racism is the main thematic question of the novel, especially the problem of Antisemitism. Therefore, many of the characters discuss overtly racist ideas and supremacy, and many of the characters suffer at the violent hands of angry, hateful bigots.
The motif of assault and violence
When communities become tribalized, they become fractured, and as long as there is at least one person willing to start violence, a never-ending cycle of violence and tribal warfare can begin. For instance, one might consider gang violence to be a kind of civil warfare. This appears in the story in the form of traumatic, violent assaults which occur in differing situations and to different extents.
The allegory of the scapegoat
The allegory of the scapegoat is an important part of Christian theology, with the gospel being the primary depiction of the archetype. Essentially, Newman is being forced to be a Jewish scapegoat (a punching bag for his community's anger and hatred), against his will. In other words, his punishment is to be submitted to a messianic form of service without the virtue that would have protected him.
The motif of paranoia
One of the unfortunate effects of racism in the community is that no one gets to feel safe anymore. Finkelstein and Newman both become wracked by paranoia. Even Newman's own company betrays him because, after all, he does look a little Jewish in his new glasses. This terrible willingness to serve ones own interests at the drop of a hat is what is called paranoia.
The parable of the racist Christian
When Gertrude gets called a Jew, she doesn't respond by questioning what is offensive about Judaism. She responds by becoming offended by the very suggestion that she might resemble a Jew, because she's a Christian. However, Christianity is literally the practice of trying to resemble a Jew, namely the historical person of Jesus Christ. This constitutes a betrayal of her own savior, like Peter at the cross.
