Former Prot Here:
Just leave him be. The mental gymnastics one must engage in to hold such warped theology stable in one's mind are exhausting. You have to physically keep plugging your ears and covering your eyes to painfully obvious contradictions at every turn.
It's scarey. And when you consider the degree of anti-Catholic / anti-Orthodox brainwashing they've been subjected to, there's nothing scarier than to take a peek into the truth of Christian history.