Why did Jimmy make sure to finish his ice cream?

Jimmy's been playing with fire—literally. The devil makes mischief for idle hands, as they say, and one day Jimmy, in what's presumably an effort to cure boredom, starts cutting off bits of his hair and burning them with his mother's lighter. It's a fascinating experience for Jimmy to watch his hair go all frizzly and squiggly. But when his mom finds out, she's not amused. Jimmy's dad gets involved and soon he and his wife are having a blazing row. No pun intended.
In a way, Jimmy feels kind of glad that his parents are arguing with each other; it means he won't get punished. At the same time, he also feels a little guilty for being the cause of their row. Anyway, after his parents are finished arguing, Jimmy's treated to a bowl of raspberry ripple ice-cream by his father. Jimmy makes sure to eat all of his up, as he wants to show his father that everything's ok. At this moment, the last thing that Jimmy wants to do is to make his father think he was feeling bad over having provoked the row. This is an opportunity for cheery father and son bonding, not for upset and recrimination.