I think we can guess that the Pax did not know that he HAD to obey the crew command and it looks very much like crew did not spend too long explaining the details of the Ts&Cs to him. So, the fact that he reacted badly may have been because he did not know the rules and the ones who knew the rules were so used to them - that they didn't stop to explain.
Likewise, the stock market has not waited for an explanation. Just look at their graph for the last 36 hours. All other carriers must be very grateful to United for the free lesson.