Although I side with you guys on an emotional level ("Why ruin a good car?"); The fact is, the car belongs to him, and he is free to do with it as he wishes.
What we all need is for someone to come here and post pictures of a Model A hot rod that was converted back to stock. That would make us all feel better! For some reason, it's always the other way around...
If it makes you guys feel any better, my 31 Tudor was saved from becoming a hot rod. Seller sold it to us rather than the rodder even though he inquired first, simply because we promised to finish restoring it to stock condition.