You could put the proof in front of his face and he will deny it. His entire existence would become worthless if he admitted the truth.
He will die ignorant. We have to accept this.
Except that the evidence at https://bitcointalksearch.org/topic/m.10718395 which proves that God exists is being proven by scientists using the scientific method, continuously, on a daily basis, even though they don't express it this way.
Why would anyone think that God doesn't exist since all the evidence of the whole universe proves that He does? The above link shows the proof.