"A poor customer service attitude at United resulting in law enforcement being called to resolve a contract dispute" seemed to downplay the direct connection between his refusal to obey crewmember instructions and the calling of law enforcement.
Please see my post #176 above. I believe I made it clear I did not wish to ascribe any particular levels of importance to one or another factor in that post. I also did not there ascribe causal connections between them.
If one wants to discuss the relative contributions of these factors and their potential causal connections, I would suggest first reading the Wikipedia overview at
https://en.wikipedia.org/wiki/United_Express_Flight_3411_incident . This contains an overview and links to interviews with other passengers on the plane (one can track down the original sources from there if one wishes not to trust Wikipedia on this.)
Those quotes overwhelmingly assign primary blame for this escalation in violence on the UA supervisor Danielle Hill, whose apparent power struggle over this issue escalated the level of confrontation significantly. She evidently made a snap judgement to call law enforcement rather than considering alternatives or some other way of diplomatically resolving the situation.
That set of facts argues, I think strongly, that the poor customer service attitude of UA, manifested by employing a supervisor such as Ms. Hill, was a primary contributing factor.
At that point Dr. Dao could be regarded as in a civil negotiation to resolve what he, with some reasonable cause, believed was a valid contract dispute. Subsequently, in the presence of a hostile and inflexible attitude by Ms. Hill and with the police, he likely violated a Federal regulation or law.
It is multi-causal, since if Ms. Hill had been better at dealing with this, or Dr. Dao had realized it was then time to just give it up and find another way home, the violence would not have occurred.
Since Ms. Hill was supposedly the professional in dealing with these situations (which Dr. Dao was not) and since her bad actions preceded those of Dr. Dao, I am inclined to assign greater fault to her. The counter-argument if trying to finely parse blame would be that it is worse to break a Federal regulation or law than it is to simply be a supervisor with a terrible attitude.
My point when entering this thread, however, was somewhat different. Namely that it was a bad idea to escalate the situation by calling the police when other likely less violent alternatives were available. It appears Ms. Hill did not give much serious thought to that and was encouraged in her attitude by UA. It appears her attitude was one of being annoyed by the last minute request to put these 4 employees on the plane, that she took it out on the passengers, and then adopted a "I'll show you whose boss" attitude with Dr. Dao.