"But if you weren't eating ________, you wouldn't be fat, so you are lying!"
Oh, I love this one so much. This is where we just can't win. We are faced with nasty hyperbole about hamburgers and donuts, and when we say,"That's just not the case," we're accused of lying. Fat haters tend to assume that a person being fat is enough evidence to convict them of excessive eating, incorrect eating, or both. There are two major problems with this, though.
The first problem is that a person's size is not any kind of proof that they are eating the wrong things, or eating too much. While the haters will deny this until they are foaming at the mouth, it is well documented that dieting makes people fatter in the long run. Those who DO manage to remain thin after losing weight do so at the cost of having to maintain a very low calorie diet. This kind of diet requires a great deal of effort, because fighting against hunger and the brain's attempts to get us to eat more is very very difficult. It's a form of suffering. If people choose to suffer in order to become and stay thin, then that is their choice--but I am of the opinion that suffering is a bad thing, and I'd rather have less of it in my life.
Unfortunately, some people take offense at those of us who do not choose to suffer. They don't think it's fair; after all, they've put in all this effort, so why should someone else be allowed to opt out? And, rather than give up their own suffering, they instead decide that, if we aren't going to do it voluntarily, then by god they'll make us suffer, either by following the same path they did, or by social stigmatism and outright cruelty. Here's the thing, folks: Just become something is difficult, it does not mean that it is worthwhile or admirable. If it became socially acceptable to shove dock spiders up your nostrils, I would have to take a pass on that as well.
The second problem I have with accusing people of bad eating, and then of lying about bad eating, is that what othe people eat isn't someone else's business. It amazes me the number of people who are pro-choice about abortion, yet will condemn someone for eating a cupcake. Whatever happened to the idea that what you do with your body is your business? What you put into your body is your business? Honestly, I could give you a million and one reasons why eating meat makes you a murderer (JUST AN EXAMPLE, FOLKS), but I'd rather people come to their own conclusions about how they feel about the various ethical, environmental, and other considerations regarding eating animals.
If I'm interested in whether or not eating cupcakes and carrot sticks is a good idea, the information is out there, and I can read it and make up my own mind. But if you're screaming at me about having a piece of chocolate, and telling me that enjoying a treat is the reason I am not worthy of basic courtesy? And that eating one chocolate means that all I do is sit around eating chocolates all day? I'm going to tell you how much of a crass moron you are, and you'll totally deserve it.
Plain and simple, unless you are following someone around every moment of every day, you really don't know what they do or do not eat, regardless of the size of their body. And, even if you did, and you found that, yes, that fat girl is actually eating a gallon of ice cream and four dozen donuts every three hours? It's still not any of your goddamned business, and it's not an excuse to dehumanize her.