FlapsOne has it exactly right.
The important words in CAP371 are "may" and "at his discretion". I have never felt unable to continue into discretion (yet), but members of my crew have, and I always choose not to exercise my discretion in those cases.
When faced with the inevitable phone call/tea and biscuits, I just say that I "chose not to exercise my discretion, having taken into account the circumstances of my crew", and decline to discuss those circumstances.
They may rant and threaten, but in the end there is nothing they can do.