It's bad to strike something in anger.
Luigi was upset because he thought his brother Mario got the better Xmas gift.
Luigi wants to point out he's upset.
Luigi tries to explain that Mario got a much better present than he did.
Luigi tries to make a running punch on the punching bag, but he misses and hits the wall.
Luigi's parents are upset but as Luigi has broken no rules he is not punished.
Luigi ends up paying for a broken wall out of his allowance.