R. Joseph Hoffmann over at The New Oxonian has recently been posting a series of biting critiques of the recent (though semi-annual) surge in Jesus Mythicism. His latest post is called "The Passion of the Christ-Deniers," and can be found here. Hoffmann suggests that the urge for mythicists to "prove" the non-existence of a historical Jesus comes from an overreaction against conservative fundamentalist theology and high ecclesial bureaucracy, and points the finger at folks on both sides of the aisle (so to speak).
I agree with most of Hoffmann's sentiments. The question of a historical figure's existence is not an inherently theological issue, nor should it be. I have seen few non-Muslims and non-Buddhists question the historicity of Mohammed or Siddharta Gautama. However, I do find it perfectly reasonable to allow one's theological perspective to be informed by historical questions, and using them to help to frame his or her perception of the past.