In the argument, we see that lines 3 and 10, show how the characters BOTH taunt each other and insult each other in a way. In line 3, we see that Toby is clearly taunting Shelene by holding up the cards and dropping them all on the floor.
Then, in the last line (10), we see that Shelene is taunting Toby about how he has to do homework, and she doesn't. These both are shown in a playful manner but intend to insult and taunt the other character. After line 3, we see that Shelene is clearly hurt by his words.
The overriding theme of The Storyteller is the concept of moral choices. The book explores how much choice people actually have when it comes to moral issues and how those choices are made and/or justified.
