Hi Muck! Um- you sort of just defined what a *Diest* is, so nope - not "ridiculous" at all.  Look no further than what Jefferson himself thought of Christ and his following of him:

"I am a Christian in the only sense in which He wished anyone to be: sincerely attached to His doctrines in preference to all others."

"I am a real Christian – that is to say, a disciple of the doctrines of Jesus Christ."

This solidifies both the Diest view and what's been said here all along.  Hope this helps!