Passengers who are handicapped and have special needs know they are expected to inform the airline of their special needs. It has become a problem when a person requires 2 seats and only buys 1 ticket and doesn't inform the airlines of their special needs. They had to do something. The only time they are going to charge the extra fare is when the plane is full. It's rude to assume that it's perfectly ok for your obesity to cause another passenger to be bumped off the flight. The airline would have to refund the money to that passenger or provide them with another ticket. The airlines had to do something to stop this.
I am sincerely sorry for those who have thyroid problems that cause obesity, it's as bad as any other handicap. There's nothing cheap about being handicapped. Some have to have special equipment installed in their house just to adapt. Buying an extra seat is no different. You have to realize that you're handicapped and you will be treated differently because of your special needs. It's sad to say, but it's true. Thanks to a few rude passengers who bought one ticket knowing full well that they needed two, this policy now has to be enforced.