Bingo. Hit the nail on the head right there. I know of no way that this story undercuts Jesus the Man, Jesus the Son of God, Jesus the Prophet, or Jesus the Rabbi. It does not claim anything about the man was false. Its greatest heresy is proclaiming the Catholic Church knew things about Jesus that it kept from the masses.
As if they haven't done that anyway.
I heartily recommend two comedies for you all in the vein of The Da Vinci Code: Dogma and Hudson Hawk. Go watch these two movies and tell me Dan Brown didn't take more from these films than he did from Baigent & Leigh's research. At least they got cited.