So you’ve moved past the absurd “special treatment” argument? Good.
As to your question; what does that matter? Does obeying the flight attendant somehow hurt Coulter’s case in your view? Should she have refused to move? If she had refused then perhaps she would have been forcibly removed.
This is (or should be) very simple. Does Delta allow passengers to pre-book and select specific seats? If so, then did Ann Coulter pre-book and select this specific seat? If so, why was she removed from that seat? Was it mistakenly booked twice? If not, then why was someone who did not pre-book and select that specific seat given the seat over the person who did? Is there a clause in the purchase of pre-selected seats that says Delta can arbitrarily refuse to honor them? Even if so, an explanation of why isn’t unreasonable to ask for. So why did Delta refuse to honor a customer’s purchase?
Maybe some video of the incident will be released that sheds some light on this. Surely someone recorded it. Barring that, or some reasonable justification from Delta, Coulter is justified in being upset. She didn’t get what she paid for.
Delta has the right to ask a person to change seats.
Ann has a right to a refund for the difference in costs.