Depends how entirely stupid the opinion is, I'd say. I'd argue that acting with decorum could well go out of the window in such a situation. For various reasons, I find it difficult to criticise somebody for refusing to move given the many other people on the aircraft, the allegedly dubious selection of Asian customers asked to depart, as well as the paltry offering of money to leave the plane. Furthermore, he could have had even stronger reasons for wanting to stay on the aeroplane than merely getting to work. These details will all become clearer after the incident, but it's easy to criticise the actions of a near-70 year old man for refusing to move without knowing the finer details.
Ultimately, where do UA draw the line? What if a person soon-to-be-ejected is flying to spend time with a dying relative? What if their partner has gone into labour? What if they have spent a small fortune trying to be somewhere at a certain time on a certain day that simply mustn't be rearranged? If a person has paid money to fly on an aeroplane, have sat down on said aeroplane, and are randomly (or not randomly) told to leave the aircraft then yes, I can totally understand why they will sit there and argue the toss until the bitter end. Should that result in being knocked unconscious and violently assaulted? We both know the answer to this is no. I'm finding it difficult pointing too many fingers at the old fella, I'll be honest.