Hi, I'm new here. I have lived on both sides of this issue. For my career, I have been a management consultant who lived on airplanes and planned my seat to a T. I am also married to a man with MS, and he now uses a wheelchair full-time.
Here's what I wonder: why wouldn't the FA's have made an announcement in the FC cabin that they need someone to volunteer to give up an aisle seat so that the Dad could sit next to his daughter? Surely someone would have been willing to do it. I understand the need, but it does feel rather unfortunate that this one passenger in 6B had to be put on the spot.
I also wonder why that family didn't claim the bulkhead row? We have never had a problem asking for and getting the bulkhead seats.