For God, justice doesn't mean simple fairness, flattening everything out so it's the same. Justice means seeking for everyone what they need to flourish.
The problem for people of Christian faith is that there really aren't very many good answers to the question of "why" in the Bible.
The establishment of justice is one of the most important Baha'i teachings. Justice in this life and on this Earth is critically important. It is the antidote to bigotry and hatred, disunity and discord.