You are correct with regard to the Unite membership and how much more of their subs they want to be directed to this dispute, if it was not for the action in punishing workers for taking IA.
Somehow I just don't see the 2 million Unite members who do not work in the airline industry seeing the BA dispute quite this way. I have yet to meet anyone who sees cheap fares for airline staff as a fundamental human right, and certainly not one they'd want their money spending to defend.
You are in the bizarre position of defending a dispute that is now all about getting back a perk, actually about getting the queuing order for that perk (the perk itself was offered to be returned). The perk would not have been threatened if staff had accepted an earlier (better) offer than the one many of them now claim they would have accepted if only BA had included full reinstatement of their travel perk.