I can see the rationale behind this argument, namely, the world is the result of God's will. Thus, if something does not happen to be the case in the world, it means that God does not want it to be. However, the argument can lead to unwanted results. Let us, for instance, suppose that the scholars of evolution who claim that cheating is part of our evolutionary skills are right (for a reader-friendly introduction to the topic, see here). Would one still say that this is a sign of the will of God?
The ought-is distinction seems to me a more rational (i.e., less self-contradictory) approach to the topic.
Am I overlooking a way which could make ontology a good support for one's belief in God (supposed this has to be rationally justifiable)?
On the ought-is distinction and one's belief in God, see this post and this one.