@Procrustes,
Steep learning curve indeed.
But we know from history that if there is anything people are bad at when it comes to religion, it is admitting that their beliefs are wrong. It's entirely understandable, since religious beliefs are often deeply rooted, and utterly entangled with the believer's emotional state, making the altering of these beliefs a traumatizing experience.
So would they abandon their faith if Jesus told them it was wrong?
Some would, of course. But more would simply tell themselves this new Jesus was a fraud.