Why do so many atheists believe that Jesus never existed?

I mean come on, even Richard Dawkins and Christopher Hitchens believe that Jesus was an actual person. Weather or not you believe he is a prophet or the son of god, there is plenty of historical evidence to show that Jesus was a historical figure. I can't believe that so many atheists are duped by that Zeitgeist movie. I myself am an agnostic and I also study history a lot, and it is shameful that so many other atheists deny history.