Here are two issues to consider.
First, why didn't United simply increase the offer to pay more for volunteers to leave? I think this is the same reason why United didn't simply buy tickets on another flight for its employees, or why United didn't charter a van or come up with some other way of transportation. It is because of corporate culture. A large, hierarchical and bureaucratic company, tied up with regulations and union contracts, fosters a culture in which individual initiative and smart decision-making is discouraged due to psychological and risk-aversion reasons, which is ironic because now a large risk has been created by sticking to standard operating procedure. This is the reason why the manager in charge did not make an alternative choice; because he is just as myopic as the CEO of United Airlines, who responded by defending United’s aggressive actions. The overreaction by United and follow-up reaction by its CEO perfectly reflect the ironclad company culture of pigheadedness.
Second, why did Dr. Dao fail to comply with United’s, and later the airport police’s directives for him to leave the plane? Certainly, any person would be incensed at being told to leave a flight, especially if that person is a doctor who really needed to see patients the next day, especially if that person is a minority targeted for perceived docility. Moreover, although Dr. Dao may not have known this (nor anyone outside of certain contract specialists), even United's own Contract of Carriage suggests that United was in the wrong – though passengers could be denied boarding on oversold flights (Rule 25), there is a clear distinction between that and taking a passenger off a flight he has already boarded (Rule 21), the latter of which was what had happened as Dr. Dao was already on the plane when he was dragged off.
Regardless, what about what else might have been swimming around in Dr. Dao’s mind? In court, a person’s criminal history is considered if that person was convicted of certain types of crimes. Here, Dr. Dao is himself no angel (though certainly no excuse for United to have him beat up). Dao was convicted in 2005 for illegally dealing highly addictive opioid pain drugs in the course of soliciting a patient for sex. He then turned to poker, where he made a small fortune. In 2015, Dao’s medical license was finally restored, but he was restricted to practicing only one day a week in an outpatient facility. Dao valued his ability to practice medicine again, but what then made me question his other motives, including the possibility that he took advantage of an opportunity by provoking force to be used (we do not know when and how exactly he became injured), was that after the United incident, he made the following statement to the media:
Dao, 69, said he’s recovering in a Chicago hospital. When asked what his injuries were, he said "everything" and that he was not doing well.
Nevertheless, United has a lot to answer for as well. I will certainly boycott United regardless.