Give Him a Chance!
“And G-d said: “Should I conceal from Abraham what I am doing?!” (Genesis 18:17)
G-d had already decreed Sodom’s fate, yet He gave Abraham a chance to “convince Him” otherwise. Why the exercise in futility? Perhaps this is a lesson in how to help others develop good habits and noble character traits: Give them a chance to practice! G-d wanted Abraham to stand up to perceived injustice because that is the type of person G-d wanted him to be! You want your child to be giving? Give him a chance to give, then notice, applaud and reinforce when he does. You want your child to be a hard worker? Provide her with a challenge, then notice, praise and reinforce when she steps up to it (even if she fails).
Scolding your child for being mean will NOT encourage him to act nicely next time. Noticing and praising his next act of kindness will.