Accomodating passengers

It appears that the size of individuals is growing. See here for an animation of obesity levels in the US, and here for a BBC article on conditions in the EU. Our infrastructure is matched to accommodate the average size of people, however it appears as if the average is increasing, which strains the infrastructure. See for example here, here, or here. This story is just as relevant when it comes to air travel, and the recent incident with director Kevin Smith will most likely increase in occurrence. Kevin was asked to deplane a flight on Southwest that he was on standby for because he got the last remaining seat, while he held 2 seats for a later flight. Southwest has a policy requiring customers of size to purchase 2 tickets, 1 of which will be refunded if there is an empty seat in the cabin when the door closes.

I got curious to know the policy of other airlines. I discovered that there is inconsistency on this matter. I did come across this general overview. Actually, it was pretty hard to find an airline's policy on this matter in general. Airlines such as Delta, SAS, JetBlue, Lufthansa, easyJet, British Airways did not have any guidelines on this specific matter, although there were for customers requiring assistance (e.g. visual or hearing impaired). Here are some other airlines' policies though:
Southwest
American Airlines
Virgin America

I only checked a handful of carriers, but I found it challenging to get a clear picture of what the guidelines are on some airlines.

As far as the incident with Kevin Smith goes it is a tough call. There are statements that he fits in the seat with the armrests down, and does not require a seat belt extender. So, it would appear that he adheres to the guidelines of the airline. However, he states that he often buys 2 tickets because he enjoys the extra room and can afford it, however I do not believe that. Picture it this way, if Kevin has 2 seats, and there is a single empty seat in the cabin and a standby passenger they will give that seat to the standby. Airlines that use the standby or overbooking principle are not in the habit of allowing seats to go empty. Southwest obviously uses the standby principle as Kevin benefited from it himself.

The sad thing is that these types of confrontations will most likely increase in the future, and they are as uncomfortable and challenging to the passenger as well as the crew.