How about Rome's best kept secret: Nero never existed. The government made him up out of necessity.
Evolution's best kept secret: Darwin never existed. His followers made him up out of necessity.
Like C.S. Lewis said, the existence of the largest religion in the world cannot be explained if Christ was not raised from the dead, and in order to be raised, he had to exist. And we have the testimony of many secular sources to satisfy all but the skeptic who covers his eyes with his hands. See Jesus & Christian Origins Outside the New Testament by F.F. Bruce.
What's disturbing is not that some fool decided to make a movie declaring that Christ never existed. What's disturbing is that people will believe it if the director can get a guest spot on TRL.