I see these references used a lot in this case...
"He refused a lawful command by the crew..."
"Passengers who fail to comply with or interfere with the duties of the members of the flight crew, federal regulations, or security directives;"
"The crew" in this case would be one of the pilots or flight attendants correct?
Do we know for a fact the doctor disobeyed a direct order to disembark from a crew member of the flight or did this escalate after a gate agent talked to him?
If it was a gate agent I don't see how he broke any law.