Nothing you said applied in this case.
This was not an oversale condition. UA will say it was, but they booked their employees after they knew the plane for full.
Also, Dr Dao was already boarded, which means UA illegally denied transport of a paid passenger. UA will argue that it was really just a denial of boarding since the flight had not pushed off.
Even if you buy that line-of-bull, UA did not follow the proper procedure to select passengers for involuntarily denial of boarding. Hint, late boarding, non-reservation, non-fare passengers, like the UA employees are the first to go.
UA illegally ejected a passenger for their own convenience. They will rightfully pay the price.
One of the few Freepers who knows what he/she is talking about. Well done!