You have to bifurcate this incident. Most here are questioning the over book compensation policy of United. That is fair. I don't see, so far, any reason to criticize the employees. They appear to have followed all the proper procedures. If the limit is $1000, a gate agent just can't unilaterally decide to up the limit. I suspect no one at ORD has that authority. But what has everyone up in arms is the way the pax was removed. That is on the passenger and the "Chicago Aviation Security Officers" (that is what they have been called by United, I don't know if they were Chicago Police or not). The airline is not responsible for how an outside agency performs it job. If you call the police to your house because of an intruder, and the police break his arm taking him into custody, would it be fair for the suspect to sue you, or the press to bad mouth you for any misconduct on the part of one or two police officers you called to the scene?
There are lot of reasons for a last minute positive space deadhead crew. It is almost never for poor planning.
Nice list of prior bad PR moves or poor service on UAL. No one remembers them. That is the way American consumers are now. Short memories. They only know what happens to them. YOU get treated well, you come back. YOU get treated poorly, you don't come back, if it is an option. If enough passengers are asked to deplane for a deadhead crew, refuse $1000, and get violently removed by authorities, they will remember. They won't come back. If they see it on TV, not so much.