When this guy was selected “randomly” to get kicked off the plane, his past was not examined or scrutinized, and had no factor in the decision. Therefore, it’s irrelevant.
Now, suppose United had said, “We need to remove four of you from the aircraft. We will be considering your past sins, your past crimes, whether you allow neighbor children to play on your lawn, and anything else we can glean to determine which four of you are the worst scum of the earth. The four winners in that category will be dragged from the plane.” Now, in THAT case, the doctor’s past might be relevant.
But these factors were not considered at that time, and were unknown. Therefore, irrelevant in the decision.