Neville,
IMHO there's not a huge difference in a well equipped non pressurised A/C at night in the wet ex CNS or picking your way around a wall unforecast CB's over India at FL400 at night and trying to get Mumbai on HF for diversion.
It takes experience and judgment to decide what you can negotiate and what you can't.
No arguments there. The issue is not being stuck with a prop and below A100, the issue is having a culture where ops (and other pilots) accept your decision to either turn back or reschedule elsewhere. Contrary to your implied opinion, I have seen that exist in GA.