Speeedy, my understanding is that the arguments by all of the parties were somewhat more sophisticated than that.
My understanding of the argument presented was if the action was response action by Qantas, then the action was protected. Termination of protected action terminates the protected action of both Qantas and the party they are responding to. Thus the question is if the action by Qantas was response action for AIPA's action. AIPA argues that it was not, or that the court (FWA) did not put its mind sufficiently to the fact of determining if the response was to AIPA - leading to an administrative law question of jurisdiction. The respondents argue that any response is, by definition, response action and therefore FWA was not obliged to consider proportionality or disaggregate the actions of the separate parties.
The arguments on both sides were convincing. It will be interesting to see how the three judges argue their decision.