Elderlite,
I understand the question, but suppose you look at it from his point of view. He views the Bible as having authority, therefore he quotes from the Bible to come to a conclusion.
This is not a bad thing in itself.
I could quote to you from a book on astronomy and give you the reference. You might take what I say as truth because I am quoting from a published work.
In this situation, you have a book, or 66 of them, that are believed by a lot of people to be God' Word. That is all the authority they need.
The doubters and skeptics don't believe the Bible or only believe portions of it, therefore they cannot accept the Word as the final authority on anything.
This is a situation where neither side can convince the other side of their viewpoint. It's not check mate, it's stalemate.