When the gang is trying to steal the safe from the store during the riots, Gunnar encounters his father who is pulling up with he other policemen, and tries to distract him to let the others get away. When he tries to talk to his father, his father says, "You are not a Kaufman. I refuse to let you embarrass me. You can't embarrass me with poetry and your niggerish ways" (137).
This scene way very striking to me in a couple of ways. Just looking at what his father says first, "You are not a Kaufman" gives off this very hostile vibe that you would not expect from a father to a son. The fact that he is willing to completely separate himself from his son without even knowing the situations he is in seems like their relationship was already messed up. In addition, Gunnar's father see him as only a source of embarrassment. This seems weird especially when he mentions poetry because the gang he runs with and all the other gangs have resident poets, and it seems to be fairly accepted in the society, but Gunnar's father sees it as a source of embarrassment. This puts a twist on the situation where your parents are supposed to be accepting of what you want to do with your life, and his mother is fairly accepting of everything he does, but his father is angry with him for it.
The other striking phrase is when he says that Gunnar's "niggerish ways" are an embarrassment. Previously Gunnar was ecstatic when he was called the n-word, but in this context it is very insulting. The way he acts is seen as bad and unseemly, playing into the stereotype of the aggressive. uncultured black man. Gunnar's father dislikes how Gunnar acts so much that that he is willing to hurl what could be considered one of the worst insults at Gunnar. I think this insult is so bad because it is basically telling Gunnar that his identity is wrong and wont be respected by people outside of the community.
Overall, Gunnar's father dislikes Gunnar very much, enough to basically call him out as a completely different person, completely unrelated to himself. He also harbors enough animosity towards him that he is willing to call him an embarrassment, and even call his character bad.