the check-in witch literally stood up and screamed abuse into her face. She was kept for 20 minutes at the checkin desk and abused. The woman's fellow check-in staff were telling her to calm down - but not actually helping. Eventually a KLM supervisor appeared
This all sounds and embellished to me, especially when you resort to calling somebody a 'witch'. The Supervisor you referred to would also have been from the same handling agent. KL/AF only have a couple of their own employees at MAN who wouldn't get involved with issues like that.
EK do not employ their own Check-in staff either, this is handled by Dnata, who, although are owned by the same grouping, are none the less still accountable to the airline and have themselves been subjected to an improvement notice by EK on at least one occasion that I know of.
The only airline that employ their own check-in staff at MAN are Jet2.