This was "Classic Dr. Phil" so I hope the intervening years have brought you new insights and perspectives. If they haven't, here's what I wish Dr. Phil would have said:
Because no one is perfect, each and every one of us, even you, has unhealthy things in our lives.
For some, those areas of unhealthiness are PHYSICAL and/or BEHAVIORAL - things like overeating, undereating, eating unhealthy foods, exercising too little or too much, smoking, drinking alcohol to excess, addictions (drugs, gambling, pornography, internet, workaholism, etc), self-injury(cutting, etc), not getting enough sleep, etc.
For others, their areas are EMOTIONAL - things like wrong self-image (whether narcistic or self-loathing), depression, chronic anger, critical or judgemental attitudes [sound familiar Molly?], chronic negativity, obsessive thoughts, or any number of other emotional struggles or mental illnesses.
Others may have RELATIONAL unhealthiness - physically abusive relationships, verbal or mental abuse, difficulty attaching to others in a healthy way, poor boundaries with others, being excessively controlling, rage or outbursts of anger, sexual addictions or other forms on unhealthy sexual behavior, and all the other things that make friendships, marriages and family relationships hurtful instead of nurturing.
Molly, what you need to realize is that nobody WANTS to be unhealthy in any of these areas. Nobody starts out saying:
"I think I'd really enjoy the life of a junkie," OR
"I'd really love to destroy my marriage with my rage," OR
"What would really make me feel successful would be to emotional injure my children by critcizing them mercilessly." OR
"I believe being extremely overweight would be really satisfying."
Yes, these things are the result of choices (physical causes like thyroid problems notwithstanding), but rarely are they a result of deliberate action. Sometimes people are unaware of their area of unhealthiness. Rarely is that the case with the overweight, much less the morbidly obese. They are devastatingly aware of their problem. But like any addiction or emotional bad habit, or negative relational pattern, recognizing the problem and changing it are two entirely different things.
Molly, you wanted to change your judgmental attitude towards the obese, presumably because you knew that lacking compassion for others and judging them based on appearance instead were not indicators of relational health. In pursuing that attitude change, you went as far as to experience a day as an overweight person. And yet, at the end you admitted that even this was not enough to truly change your attitude or pattern.
If you struggle to change something as relatively simple as a judgmental attitude towards one group of people, can you imagine how difficult it is for obese people to lose vast amounts of weight? Doing that requires a major change of perspective before they can even begin making the many, many lifestyle changes needed for significant weight loss. You have first-hand experience on how hard it is to make one change of perspective, and you didn't even need to make any behavior changes afterwards!
The truth is, ALL OF THE ABOVE AREAS OF UNHEALTHINESS HURT AND/OR INCOVENIENCE OURSELVES AND OTHERS. Frankly, the inconvenience you or I would experience sitting next to a 300 lb seatmate pales by comparison to the damage we would experience should we encounter someone who vents their rage at the world by attacking us physically, or the heartache we'd face if we were to have a parent or spouse who put us down at every opportunity.
If you need a new perspective, train yourself to think how minor the inconvenience of being crowded compared to the damage of being truly injured by someone who has a different area of unhealthiness. And if you REALLY want a new perspective, compare the inconvenience you suffer from getting only half a seat with the damage you are dishing out by sending out those, "You lazy, selfish, fat pig," vibes to your seatmate.