The Fat Lady at the Buffet

This afternoon, I went to this buffet style place for lunch, primarily because their salad bar is really immense. I also went there because there is enough seating that I am not forced to sit too close to any Financial District douchebags in suits and ties flapping their lips at each other about shit they should have left behind in the office, or frathouse, or LL Bean Store,  or where ever it is people like that conduct business.
As I sat down with my salad, I happened to notice a morbidly obese woman sitting down and eating a lunch that consisted of 6 full plates of food.  Now, mind you, this is an establishment that offers buffet, but it's NOT all-you-can-eat.  The food is also priced by weight.
This woman had something like 40 dollars worth of crappy Financial District chow splayed out before her, and there wasn't a single vegetable anywhere on any of her plates.
The horror I felt while watching this woman eat was akin to the horror I used to feel when I'd watch my junkie friends shoot up in front of me back in my early twenties.  It's difficult and extremely uncomfortable to watch a person doing something that you know is killing them.
It's like a suicide in slow motion.
There are many people who belong to online communities that support what they like to think of as , "Fat Acceptance", or The Fatosphere, as it's more commonly known.
This is a collection of bloggers and activists who fanatically defend the right for anyone to get as fat as they want to and not be demeaned, harassed, or discriminated against because of their size.
Though they say that they are proponents of the Health at Every Size concept of body acceptance activism, they have been known to criticize and even outright delete, from their websites, any member who expresses a desire to lose weight.
Fat discrimination is too complex an issue for me to discuss with any depth and quite frankly, as a person who is only 20-30 lbs overweight at most, I also feel that I am not qualified to speak that much of it.
I may have become invisible since becoming overweight, but I certainly have never experienced the kind of cruelty the morbidly obese face, all the time, from random strangers.
Do they deserve to be mocked and marginalized for "letting themselves get like that"? Is there ever a time when any human being deserves to be mocked?
Why are fat people so frightening to us? What is it about them that we fear so much? Is it purely a pack animal reaction to poor physical health? Do we react in the same way wolf packs do when they chase off and attack the sick and weak ones?
Why aren't there more people approaching this issue from the perspective of mental illness the way we do anorexia or schizophrenia?
As I looked at this woman eating herself to death, I wondered what her story was. 
I tried not to stare, but as I looked at aoo of her plates heaped with burritos and lasagna and cakes and then at my own tiny salad bowl, I had two thoughts.
One of them was, "I wonder if I would be so disgusted if she were a skinny person sitting there with that much food"  and the other was this: "Her food probably tastes way better than mine, and I bet she's enjoying her lunch more too".