If the above story is true then the instructor needs to spend some time in reflection.
FF, it is true, my name's not DT!
It was another instructor in my club, a long time ago. I learnt from his experience and always make sure that a new student/passenger is briefed to use their right hand on the stick.
...aircraft with yokes I can fly with either hand.
Me too - I'm comfortable flying Cessnas from either seat but I have had difficulty on the rare occasions that I've flown left-seat in an aircraft with a stick and a central throttle.