You don't teach CRM I take it Bob?
Providing clear advice that remedial instruction is needed is one thing, refusing to sign the paperwork is another - but issuing threats like that is something else altogether!
Genghis, I merely said it was a suggestion (which was made at an Instructor's seminar).
That said I hardly feel that this is an occasion for touchy feely "CRM". If a pilot is clearly unsafe and refuses to take advice to undertake remedial training then I would suggest it's time for "Advocacy" - something which is part of CRM.
Maybe I've been lucky but I've never come across anyone in this respect that I would describe as "unsafe".
How would you feel if you didn't take any action and said pilot killed himself and passenger(s) a week later?