Here's a valid informal argument. Again, soundness is the question. If I react to the shape of x, then x's shape plays a role in a causal explanation of my reaction. If I react to the injustice of situation, then, by parallel, the situation's injustice must be play a role (perhaps a privative one) in a causal explanation of my reaction. I do react to the injustice of some situations. But if naturalism is true, then justice and injustice do not enter into causal explanations. Hence naturalism is false.