After several attempts to distract his young parrot from chewing on furniture, George reluctantly took an expert’s advice and gently hit the parrot’s beak whenever the bird started to chew furniture.
Judgment on George (should = opinion)
George should not have hit his pet for chewing on furniture.
Reason (since)
Chewing on furniture would not have hurt the bird.
Implicit Principle
If action X wouldn't hurt your pet, then you shouldn't hit your pet for action X.
Judgment on Carla (so)
Carla was justified in hitting her pet when it bounded into a busy street.
Reason
Now the pet enters the street only when accompanied by Carla.
Evaluate
When we read this, we might be thinking,
The author would have to say that these are two different situations; there's a meaningful difference that makes him shift his pet-hitting policy from "not cool" to "justified".
He never spells it out, but the suggested difference is that in Carla's case, the action she was trying to prevent could have easily hurt the puppy. He probably thinks, .