Your review of "The Jesus of Hellenistic History" mentions "mainstream" Christianity. This has become a misnomer in the last 50 years. The only thing "mainstreamers" retain as orthodox is their denominational names--United Methodists, Disciples of Christ, Episcopalians/Anglicans, and so on. They live in name only! Inside the sanctuaries, they are often virtually empty--even on Sundays! Their congregations shifted out of these pews and into atheism, agnosticism, cults, the occult, New Age-ism and most often into new conservative (orthodox) Christian churches.
The mainstream "liberal" theologians have simply helped their denominations to continue their own suicide.