Why is Brady such an easy foil for Drummond as he is being questioned about the Bible?

Drummond uses the opportunity to put Brady on the stand to expose Brady, who is a strict fundamentalist, as someone who does not interpret the Bible literally. He also exposes Brady as someone who considers himself to be a prophet. As a result of the questioning, the spectators laugh at Brady and walk out the courtroom. He has been made a laughingstock.