@ Piltdown Man
I understand your concerns. Now look at it from the passenger side. I would suggest that it's fairly reasonable for a passenger to consider that after they have purchased their ticket, complied with all the rules and requirements, been accepted without condition at the gate and taken their allocated (and booked) seat, the last thing they might expect is to be bumped off AT THIS STAGE of the process. Even more so if they are going to be split from the rest of their family. The bottom line here, which many seem to have forgotten, is that the airline made some sort of monumental cock-up regarding the DH crew and they expected 4 boarded passengers to give up their seats, without even the guarantee of a seat on the very next flight. That's just not right, period.