Treating people like humans? I think Teethgrinder might just have won. Creating an "us" and "them" mentality isn't helpful, particularly when there's such a grey area.
I'm not fat. I'm all in favour of teaching kids about healthy eating, exercise and how to cook a good meal from basic, cheap ingredients. I'm lucky that my parents taught me that - and when I was skint, which I was for a v long time, I was able to get a ten-quid veg box (shared with a flatmate), value rice, value pasta, bag of cash 'n' carry lentils, and eat for under a tenner a week. It was boring but it was pretty healthy.
What I am very strongly not in favour of, and I apologise if the hyperbole went overboard, is creating this "other" category in which we dehumanise the other and it is permissible to point and laugh in the street, as one poster suggested earlier would be a good way to get fat people to recognise social stigma and slim down a bit.
All that does is to give individuals the belief that they are allowed to make snap value judgements on others and then bully them. It doesn't actually matter whether you're pointing-and-laughing at the obese, at smokers, at drunks, or grabbing your pitchfork and looking for paedophiles: it's all the same continuum of a belief that you can enforce your own values on other people via the medium of street abuse.
To put that into a forum context, it's the same attitude that leads motorists to use punishment passes or spray water out the windows at us as we're riding our bikes. The same attitude that leads to people being egged or worse, shoved, at best, gerronthefuggincyclePAAAATH yells. Those people aren't necessarily BAD people but they do believe that their views on what's best for us (riding in single file on a cycle path is safer for us and will lead to us needing less of their tax for NHS treatment and / or less of their insurance if they accidentally hit us, therefore it is better for society that we do so) mean that they can shout abuse at us.
(Before anyone says that motorists who behave like that are behaving illegally but calling taunts at someone in the street isn't - actually, it's an offence under s.5 of the Public Order Act to cause someone harassment alarm or distress. It's not always vigorously prosecuted - there's another parallel - but it is illegal.)
It's not fun being Other, in any capacity. Not as a cyclist and not as a fattie. I've walked down the street with a former colleague who was a bit of a ten-ton nelly, but when people were abusive to her, which they were, they didn't know she'd already lost a lot of weight. The street harassment did very little to persuade her to keep up with the diet and exercise.