"This man went from paying passenger to disruptive passenger the moment he refused a reasonable request to remove himself from the aeroplane."
The court case, if it comes to that, will be decided on that "reasonable". Is it reasonable for an already embarked passenger to be disembarked because of the failure of an airline to provide necessary transport for its staff, transport that could be provided in a range of other ways? Because if United want to argue in court that you are disruptive the moment you refuse an instruction to leave the plane for the convenience of its staff, and that justifies a beating, then the court hearing is going to be a daily
PR disaster for as long as it goes on.
The Chicago Police Department have suspended their employee pending investigation, so they clearly don't have United's confidence in the righteousness of the events. It's going to be very, very interesting to hear precisely what United staff said to the CPD in order to have them come on board, and what account they gave of the passenger's behaviour prior to the arrival of the police. Because if it turns out that they over-egged their account in order to involve the police in what was up to that point a civil issue, a court will regard that as a smoking gun.