DUmmies just love 'equality' until it affects them personally. Ill be honest , I HATE flying with a passion. With that being said, Airlines are in the freight business - they plan on an average load weight to work the math necessary to insure a safe flight. If the flight is full of super-sized people, it changes the formula. When a passenger takes more luggage with them then expected, they get to pay extra. The same should be true for deluxe model humans.
The fact that it annoys the large person's seat-neighbors takes second place to the fact that more weight=change in flight dynamics and fuel consumption.