For me, it's a question of whether we are approaching the issue as a matter of religious studies or of history. If the former, I think it's not uncommon to accept the existence of Jesus not on faith, as it were, but simply to provide a baseline. Kind of like accepting that Shakespeare, not Bacon, filled all those thick books with plays. It provides a starting point which, while not required, can be helpful as long as one bears in mind that it's an assumption.

But if the latter, I'd expect a much greater measure of skepticism. If your interpretation of the evidence is that it's either inconclusive or lacking, then that becomes your starting point: Jesus as myth.

Personally I think both approaches can be instructive, and are simply indicative of two different disciplines--secular religious studies on one hand, history on the other.