This gentleman, unfortunately, can't tell the difference between fiction and scholarship. Say it with me "THE DA VINCI CODE IS FICTION." It bears as much relationship to reality as Tom Clancy's work, which is to say, it's loosely based in the world we currently inhabit.
So, most of his criticisms are moot.
What I found interesting was towards the bottom:
The average high-school educated Christian would have known that the Gnostic gospels represent the legendary phase of Christianity. Jesus Christ, among other things, was a human being, lived a human life at a specific point in human history, was sentenced to a particularly hideous death on the charge of blasphemy and, according the records left by his followers, rose triumphant over death itself – "beating down death," as the Orthodox Christians say, "by death," i.e., by his own death.
And so, this legendary phase of Christianity can be safely disregarded? Like we disregard our own American legends of The Founding Fathers? Davy Crockett? Sam Adams? Or Rome disregarded Romulus and Remus? Aeneas?
These legends serve a purpose, as well. They tell us not only about Jesus, but about ourselves. The inner and outer worlds unite in Myth, which is in many ways more interesting than history. History is (can be) propaganda. Myth is soulwork.
As a Christian, I would think he'd be concerned about that.