Being certain of something he believes doesn't make him narrow minded. If I was sure 2+2=4 but there was some new big long and complicated concept that was thought to prove otherwise, I would never believe it. Does that make me narrow-minded? no, it makes me certain.
See this is why i think you're both idiots.
Let me explain what has just happened:
He talked about open mindedness
I linked him to a video explaining the true definition of open mindedness
He refused to watch the video and justified it with "Nothing will draw me from my faith"
It's a near perfect example of narrow/closed mindedness. Being certain means you're certain. Rejecting all other sides of an argument before you even examine them is narrow mindedness.