Misquote. The full real quote is:
"I am a real Christian, that is to say, a disciple of the doctrines of Jesus, very different from the Platonists, who call me infidel and themselves Christians and preachers of the gospel, while they draw all their characteristic dogmas from what its Author never said nor saw. "Jefferson believed in the goodness of what Jesus taught, which makes sense because who couldn't? But he believed that Christianity as developed up until his time, and the Christians practicing it, were truly warped, straying far from his teachings. Notice also that he said he was a disciple of Jesus' doctrines, not of Jesus himself.
I'm surprised the author didn't pull out the fraudulent Washington quote too.