I do hope in your last paragraph you are not trying to say the pilot is in the right
The only thing that the pilot did wrong was to continue to make requests. Far better to give up on a lost cause and either just turn or perhaps better to declare an emergency and turn.
If the weather needed to be avoided for safety then there would never be an option of not avoiding it.
If I need to avoid weather then I will avoid weather. In busy airspace I don't avoid every bit of cumulus that might cause a bump. If I ask to avoid weather in the LTMA there is a safety reason for my request.
If you have aircraft to my right on a parallel with min radar separation and I report that I have to turn right to avoid weather then you have to accept that you now have to move that other traffic or end up with less than min separation.
When I can see a CB ahead I am never going to ever fly into it. I will fly round it or do a 180. I don't really care as long as I am never inside that CB.
Part of the problem is that ATC can't see any of the weather. I can see a CB ahead and I know that if I move 0.5 to 1nm further right of the current track, I can avoid. However, what I request is 20 degrees right to avoid because this is the way that it is done. You don't know that I only need to move a small bit right of track and assume that this new track is going to go on for God knows how long.
I have previously done orbits, diverted miles off track and a few times even flown a new route to avoid CBs. I have never been refused such a request in any of the worlds major TMAs including London.
That is why I am so shocked to hear that an ATCO could take such a risk with a flight by forcing that flight to fly in weather that the pilot requested to avoid.
I think that ATC attitude in this case mirrors the Captain of the ship in this video;
YouTube - Battleship VS Lighthouse
Regards,
DFC