That stuff is very interesting. Your point about motivate teachers is fruitful. I'm adjusting my belief that there was a Jesus. That said, I learned of the historical Jesus thesis from my Rabbi, who I don't think had a motivation to be pro-Jesus. And he didn't sugarcoat religion with me (he introduced me to such anti-religious ideas like the problem of evil and the problem of miracles).
That said, I can't give very much weight to docetism, (or Gnosticism generally) because they lost the ideological/theological battle. (Wikipedia is quite coy, saying that "some Christians" think it's heretical. The Nicene Creed is a flat-out rejection of docetism, so I think it's safe to say most Christians reject it).
And generally, I don't expect much historical evidence of Jesus, because he wasn't that important in his lifetime. As ArisKatsaris says
There exist only two non-biblical pieces of evidence for the existence of Pontius Pilate -- and he was the damn Prefect of Judaea for Cthulhu's sake. How much "direct evidence" do you expect for a rather Jewish-cult-leader, one of possibly dozen such groups the time?
In other words, the assertion in Mark that Jesus was followed around by scribes is a pious lie that can easily be explained without asserting that Jesus never existed.
That docetism lost out isn't really the key point.
Consider the general case: there's some property P that is observable (for example, having a physical body). At time T, there's no agreement that I have P. At time T+ 200 years, there's agreement that I had P at T.
It seems to me that the lack of agreement about P at T is important evidence here, regardless of what agreement other people come to about P at (T+200).
To break up the awkward silence at the start of a recent Overcoming Bias meetup, I asked everyone present to tell their rationalist origin story - a key event or fact that played a role in their first beginning to aspire to rationality. This worked surprisingly well (and I would recommend it for future meetups).
I think I've already told enough of my own origin story on Overcoming Bias: how I was digging in my parents' yard as a kid and found a tarnished silver amulet inscribed with Bayes's Theorem, and how I wore it to bed that night and dreamed of a woman in white, holding an ancient leather-bound book called Judgment Under Uncertainty: Heuristics and Biases (eds. D. Kahneman, P. Slovic, and A. Tversky, 1982)... but there's no need to go into that again.
So, seriously... how did you originally go down that road?
Added: For some odd reason, many of the commenters here seem to have had a single experience in common - namely, at some point, encountering Overcoming Bias... But I'm especially interested in what it takes to get the transition started - crossing the first divide. This would be very valuable knowledge if it can be generalized. If that did happen at OB, please try to specify what was the crucial "Aha!" insight (down to the specific post if possible).