What should United Airlines' PR response be having done the unimaginable?

Let’s be clear. Dragging a 69-year old doctor off a plane so that one of your employees can take his seat is always going to be an unmitigated reputational disaster. No response you can possibly offer up, no matter how skilfully it is framed, is going to wipe away the harm. 
But what United has proved is that it is indeed possible to do the unimaginable -and to make a situation where you assault your customers even worse. 
What was wrong with their response? I’d highlight t