From the explicit prohibition against the destruction of fruit trees, our sages deduced that it is all the more forbidden to destroy the fruits themselves.
Justice is a judgement that is both fair and forgiving. Justice is not done until everyone is satisfied, even those who offend us and must be punished by us. You can see, by what we have done with these two boys, that justice is not only the way we punish those who do wrong. It is also the way we try to save them.