I do think she would have been, if not “justified”, then “excused” if she had tried to strike him, as his behavior would likely be considered inciting. And anything he did in response to having been struck would have justified restraining him.

But there would have to be some kind of physical altercation involving him before they could pull out the duct tape.

They definitely should have asked for a volunteer to swap seats with her. An air marshall could have arrested and handcuffed him.