@Frank Apisa,
I agree that the message is more important than the messenger. The thing is that, as you perhaps imply, spreading doubt about the messenger's historical existence (maliciously, I repeat -- their arguments have little to do with facts as I have shown) result in debasing the gospels entirely, making them fake documents, forgeries. Therefore it decredibilise the message and makes any attempt by humanists and secular people to use any pieces of wisdom there might be in it.
That's why the historicity of Jesus is important to a secular humanist like me: he proposed a new ethic which has historical and philosophical and moral importance. I care about the message and, and I believe there's ample evidence a precise guy -- a Jew from Galilea as it turned out -- actually said it.
And just to be clear, I don't think he was a god. IMO he was a bastard, an outcast, an unruly yeshiva student, yet brilliant. Evidently likable, crazy if you will judge him rationally, yet very courageous. And ultimately influential beyond any other man perhaps.