I don't know if you can call it that unless the child has been harassed himself, but kids should know better than to pinch others in the butt. All parents should be having the "don't let people touch you here" and the "don't ever touch people" there speech with their children and this type of thing would be unlikely to happen. The kid probably had it happen to him, he was dared by an older sibling, or saw it on tv so he did it himself. The school should lighten up and the dad should have already had the "no touch" talk with him. Both are wrong.
Read it here.