The police do not have to demand to see the contract, all they have to have is an agent of the Airlines telling them the man is an unwelcome guest, and then it becomes within their legal authority to remove him.
There is even a question on whether or not they could even legally be on the plane.
And you can prove this? Please provide your proof that they were not "Police." If you can prove this point, your larger point might be valid. So far as I have found on a quick search, they were police.
There is even a question on whether or not they could even legally be on the plane.
That doesn't even make sense on the face of it. You are trying to make the argument that a flight crew would call unauthorized people on their plane to drag off an unwanted guest.
Well why would they call unauthorized people instead of authorized people? That is just silly on the face of it.
Were the actual legal authorities too busy or unavailable? Seems like there would be a need to have some actual police at the Chicago Airport, but that's just me.