Well, the other thing I find funny is that DVC is not the first book to raise the notion that Jesus' life was anything other than how it is described in the Bible.
For example, one of my favorite novels, The Light of Other Days, by Arthur C. Clarke (a known atheist) and Stephen Baxter, posits the invention of "wormcam" technology which allows one to view any place, either now or in the past. A project called the 10,000 Days is set up, wherein 10,000 volunteers each watch one day of Jesus' life and record EVERYTHING he did or said (they can read the lips of anyone they watch). Clarke and Baxter speculate that Mary was not a "virgin" in the true sense of the word, but rather a "temple virgin"; that Jesus' father was a Roman centurion; that Jesus' actual name was "Yesho ben Pantera"; that Mary hid the origin of Jesus' conception from Joseph in order to prevent shame to his family; that Jesus spent much time traveling around the Roman Empire, even as far as England, with Joseph of Arimathea; and that Jesus was sort of a New Age philosopher who wanted nothing more than for people to be nice to each other.
The only concession that Clarke and Baxter make to Jesus' possible divinity is that the moments of crucifixion remain hidden, presumably because the huge number of wormhole cameras open to that moment, both from now and from in the future, caused a disruption in the fabric of spacetime around that event... so no one can see what REALLY happened.
I guess the reason why a book like The Light of Other Days doesn't get the sort of negative attention that DVC is getting is because it's not wildly popular.