Even as an atheist (or agnostic depending on the labels one slaps on me ) I must agree with Marcus Regulus that the gospel evidence, and later writings of historians such as Tacitus, cannot be completely disregarded. If we disregard Tacitus' or Josephus' account of Jesus because they weren't there, then we must discount everything they wrote that happened prior to their own lives. One can argue that many writings of Roman historians is tainted by severe propoganda or obtained with poor source material. Still we also know that they had access to writings and other evidence which simply doesn't exist anymore. We know that Livy's account of early Rome is terribly clouded in myth, but we also understand that somewhere within his words is the basis for truth. I understand that there is no 'primary source'' evidence for Jesus, including the suspicious absence of records from Pilate, and everything else was word of mouth or provided by gospels written years after the fact. Can't we though look at the gospels in the same way that we look at other Roman 'historians'? That they are, at the very least, formed from a semi-true story that grew into a legend?
In the anti-historical Jesus world, Paul is often 'blamed' for inventing the Jesus icon to fit into his son of man religious theory, but even if that assumption by atheists is correct, the chance of him taking the story from an existing man who had been crucified for anti-establishment behavior, rather than inspiring complete fiction, is equally plausible.
All in my opinion of course.