I like the idea someone posted earlier about writing to Stephen Thompson. If it was me, I'd keep it nice and civil, telling him how much the fans have enjoyed out visits over the years. Then give him the details of the arrangements that were made with the club for banners, flags etc.
Then express disappointment about how after all the organisation was in place, how you were treated and ended up not entering the ground. Finally point out how, in the current climate, alienating supporters and missing out on the gate money etc. is not a great idea.
Thompson seems like a solid footballing man and a smart business man, so he might well take the reasoned criticism on board.
I'm sure someone from the group has already thought of this, so feel free to ignore