We really have no idea exactly what unfolded.
It appears to me that the CC was fairly calm and quiet when she relayed to the pax that they now have reason to offload him. Was she told to relay that after chatting with the Captain? Who knows? Had the gate manager already informed the crew that the pax had been difficult in the terminal? Who knows? Was the person he had swapped with in an emergency exit but unsuitable to be there? Who knows?
Whatever the situation leading up to the AFP taking over, the method used to get him off is an AFP issue, not Jetstars.
Cabin Crew don’t get paid enough or trained enough to make nuanced decisions around W&B, they are just told that it is of critical importance. At the end of the day he chose to dig his heels in and we’ve all seen the result.