Imagine you've booked a trip way in advance, and gone through the process of selecting your favourite seat on the aircraft. Then a (doubtfully well meaning) cabin attendant comes around, huffin' puffin' fatso in tow, asking you to move so that lard arse can get your seat.
Me, personally, I'd said "sure, if you upgrade me to Club". If that was denied, and disobeying an order by a crew member is unlawful, I'd ask to be involuntary denied boarding, collect the EUR 600 compensation as demanded by the EU and catch the next flight. If that was also denied, well, then I'd leave the aircraft and call the nearest tabloid newspaper and vent my guts. That usually result in a grovelling apology from the airline, and an offer of a free return ticket, if I promise to keep trap shut on the subject.
Not my problem some fat fcuker can't control their diet, and I won't be the one suffering from their poor choices.
I've always thought there should be an overwing exit mockup in the jetbridge with a sign, "You must be able to pass through this opening to board the aircraft."
Seconded!
PS
I detest the PC word "obese", and much prefer "fatso", "fat fcuker", "lard arse" or other far more derogatory terms. They choose to become fat (in 99% of cases); I choose to ridicule them.