How do you "know" they were "assessed" as unfit to continue duties? If you had ever worked in BA you might have some idea of the work ethic and culture of some work groups where the first port of call is to the union rather than line management. I've had plenty of landings well within "normal" parameters which the passengers might have felt as firm. I've been asked to apologise for a landing by a captain even though there was nothing wrong it other than being more agricultural than usual.
As for the wind, the surface wind may have been light and variable but do you know what the winds were on approach? Was there any shear? Was there an inversion?
As for heavy landing check, only needs to be raised if in the opinion of the captain, it's required or there is an ACMS print out. So, as explained above and earlier, he might well have apologised but that doesn't mean that it necessarily meets the criterion for a heavy landing check.
As for militant cabin crew? Have you no memory of recent industrial disputes within BA? Pprune is not the place to air dirty laundry but your witch hunt is mis-directed and I'll-informed.