Nonsense has it right - he should have a carer to look after him if he's too obese to fly alone. Perhaps people should be assessed somehow before flight and seats allocated accordingly. I'm not sure whether airlines would hand out upgrades simply because some people are too fat to sit in an economy seat though. Make them pay the difference when they check in?
If he defecated on a seat on a previous flight, then Eva should have put him on a ban list.