There is some dispute whether Chicago Airport had jurisdiction to even board the aircraft.
The Chicago airport is very strange it that it has 2 tiers of policing, Chicago police who are armed and can actually make an arrest report and Chicago Airport Police who are unarmed and have some ability to detain someone but have to let Chicago Police make the arrest.
Chicago Airport police were created way back when by Richard Daly as a reward to his favorite security guard to give him a job after Daly left office.
At some point it was decided to give these mall cops some sort of police academy training although abbreviated and even license them as police officers.
Their jurisdiction at the airport is limited, they can't go to non-secure areas of the baggage area for example and stick to patrolling inside the airport.
There is some dispute as to even if they can board aircraft, they have had some of their own officials say yes, others have said no. You'd think they'd want to clear that up in the decades since they have been formed.
There are calls in Chicago to disband the Chicago Airport Police since the current system is really stupid and disorganized.
I don't know what I would have done in that situation. My biggest pet peeve is ignorant authority and I've been a fighter my whole life. I just don't take crap from anybody. I would hope eventually to mellow out but at 57, perhaps not. :-)
I've run through in my head what I might have done in that situation and all scenarios turn out ugly. I guess it depends: would I ever want to fly again?
When someone in authority asks you to leave you leave. All of what you are pointing out is still unknown and you certainly don’t leave it up to each passenger to do a legal analysis in their seat while they are being asked to leave the plane. Cooperate and sort it out after, that’s the rule. If you don’t, the authorities may use reasonable man to remove you and that can incudee physical force.