dq120, I had a similar experience with a pilot who had a FAA licence and used to own a high performance light single. He wanted to fly our aircraft, so I took him on what I thought would probably be a straightforward familiarisation ride.
When he whacked the control yoke from one extreme to the other, banging against the limits, during the 'full and free' control check pre-start, the alarm bells started ringing. From then it got worse and worse - he didn't fly the aeroplane, it flew him. I had to take control during several of his landing attempts..... On another occasion we went for a short navex to learn some of the UK airspace and FIS/RIS quirks - he was hopeless. A simple circuit at an unfamiliar FISO aerodrome maxxed him out.
He went back to the US without having been cleared to fly our little PA28s.