Ametyst,
You are clearly annoyed, and, as a passenger I suppose you have every right to be.
But, I highly doubt that MAN/BE would have inconvenienced you for the sheer sake of it.
I get the impression you arrived late evening. Is it not a consideration that the aircraft you arrived on could have then theoretically finished its duties for the day, and thus the stands at MAN may have been empty upon your arrival, but, needed shortly after you passed through? The aircraft you were on may have been towed off a T3 stand anyway after disembarking, so, with the late running, meant that the original plan could not have been adhered to?
Also, were some of those gates you drove past domestic gates? They again would have been required for a specific flight just after you passed through?
I know it seems like excuses, and, could you have been informed better about the reasons behind the bussing? Yes, they could have done.
However, like I have said, I'm pretty sure someone up in the control room didn't just have a sadistic moment and thought 'I wonder how far we could push these passengers towards the edge', but, there were probably a myriad of decisions taking place behind the scenes which forced the outcome of that night.