nobody on that plane had the right to disregard authorities
It's a difference of perspective. I hate to paint with a broad brush but Europeans are far more comfortable yielding to authorities than Americans. Still having a Monarchy, who live in unimaginable opulence at tax payers expense, is something beyond the comprehension of Americans. Europeans are far more comfortable with Socialism. Giving more of your money to the government and letting them determine what is best for you. You're much more tolerant of savages invading your country without a fight.
Americans in general are not impress with a badge, a medal, a crown... Where else can a Joe the plumber get right in the President's face and tell him he's wrong?
He paid for his ticket and was seated and now United tells him the deal is off. We have the right to protest and defy authorities who has changed the rules in the middle of the game. We have the right because we make it our right. We fight back and don't automatically cower to authority.
He's already won. Got put back on the plane and United has a PR nightmare. No jury will side with United no matter how much of a scumbag the "doctor" is. United has been bullying passengers long enough. Americans have a natural sympathy for the little guy because most of us are little guys who has been pushed around.
United should have just paid whatever it took to get volunteers but they thought they could just strong arm the little guy.