Apparently there are many doctors in Kentucky that prescribe drugs in an illegal manner.
However, that has nothing to do with his being dragged off that United flight.
He knows how to put on an act.
http://www.tmz.com/2017/04/11/united-airlines-doctor-david-dao-poker-player/
Maybe he was looking for a payout...but he did not deserve to be dragged from the plane.
I would HATE getting bumped, and I would maybe yelled and screamed, but before getting dragged down the aisle my hands would have gone up and I would have started walking. The passenger controlled his own fate.