I was also under the impression that casts had to be split before flight.
It does sound as if it has been over egged but then we expect nothing less from newspapers, I have no doubt the crew weren't particularly helpful but in this case I would suggest the people he was travelling with have a lot of blame on this one.
His medical insurance should have covered extra seats if required also how did he have a fit to fly certificate without a split cast ?
If I had been travelling with his young boy I would have dealt with all of this long before i had even reached the airport to check in, but everyone loves to moan these days and blame others.