Yes, well, as I said,
It's arguable that one should have been submitted in view of the potential hazard involved with a 1.5 Tonne overloaded situation.
That's not the real point, which is that the very last-minute offload of 1.5 Tonnes of self-offloading freight indicates that a gross and serious error had been made which, if not captured as it presumably was, could have had potentially fatal consequences.
IE someone screwed up big-time. I don't expect the airline willingly to admit it publicly or release details, but I would expect the airline to be very, very polite and generous to the passengers who were offloaded as a consequence of the screwup, rather than meting out the further punishment that it evidently did.
That's what is so disgraceful, and so typical of KLM. And the passengers should pursue them through the small claims court for huge amounts, just to show them that they cannot do this in the 21st century.
Payment by Air Miles, incidentally, is not cheap or "free", it nets the airline substantial sums which you have paid for, and yopu are entitled to exactly the same treatment as anyone who has paid a fare to travel.