On the issue of whether or not a student should be prepared to question their instructor if they sense a problem, the answer is of course "maybe".
In the situation described:
the instructor decided to show us a manoeuvre that did not go as planned
unless the manouevre was something like flying upside down in an aircraft that the student knew had only a gravity feed fuel system no reasonable student wanting a bit of unusual attitude experience is going to turn down the opportunity.
He may have asked "is it dangerous?" but is unlikely to have elicited a response indicating there was a fair chance of it resulting in a spin, crash & comprehensive hospitalisation.
Obviously if the instructor said, before the manoeuvre, that he didn't expect to walk away from this one then that's a different story. Not a CRM story though, just an inflight self defence lesson.
I still fondly remember unexpectedly spiral diving out of cloud at 800 ft with a startled looking instructor who had been giving me an introduction to IMC during early stage PPL. Very valuable lesson & one I've never forgotten. Suspect he hasn't either.
Good CRM for the less experienced student, once you & the instructor accept things have become a little lively, is to keep quiet while he / she concentrates on sorting their mess out.
