Even reading this thread has made my blood pressure rise...!
I agree with some of the comments above - there is a real conflict right now between the high-falutin' personalised customer service the business class airlines trumpet in their ads, and the grim reality of arriving at the airport and taking part in a human lottery which may or may not result in sitting on the right plane, at the right time, in the expected seat.
The main issue here, however, is how one reacts to the slings and arrows of outrageous airline practice, or indeed of other similar situations in life. All the 'hyphen-rages' discussed in the media - road-rage, air-rage, whatever - are about instances where, in a situation where self-control is essential to safety, it is lost.
Fair enough, then, that if a passenger appears so implacable on check-in that he seems likely to endanger an aircraft, he does not get to travel. Yes, the judgment of who does or doesn't cross the line is in the hands of the airline - but who else, reasonably, is in a position to do it? And let's bear in mind that it is not in the interest of airlines to police this rule too forcibly: one has to assume that even the most cavalier airline prefers not to lose its customers by denying them travel.
By the way, my personal closest to causing a scene occurred last Christmas Eve, when I arrived at LGW 1 hour 45 minutes prior to a VS flight to UVF only to be told that my reserved seat in Upper Class - 3A - had become, er, a seat in Premium Economy because 'everyone had showed up'. Yes, I'd paid a truck-load of cash for the ticket; yes, it was my only major holiday last year; yes, I was hung over (it was Christmas, after all) and I'd been looking forward to a decent kip; yes, it was a bloody ridiculous thing to happen - what kind of crapola yield management cannot predict that all Upper Class pax taking a ONCE-WEEKLY FLIGHT TO THE CARIBBEAN ON CHRISTMAS EVE might, in fact, choose to show up?
However, once it became clear that no amount of grousing about my elite FF status, my support of VS as a pax since 1991, etc. etc. was going to make the slightest difference I did shut up, checking myself before saying anything too personally unpleasant to the check-in staff. And, rather than attempting to open the doors mid-flight, trying to get jiggy with one of the hosties, breaking my seat or taking a dump on the food cart (don't laugh, they've both happened!), I shut up - and took the more circumspect route of the hacked-off business customer, which has been to deprive Sir Richard of any of my custom since (for which Big shareholders should be thankful).