As a ex overweight person (Im not exactly lean but im under the overweight bracket (ive lost 69! pounds), im still planning on loosing about 10 more pounds or so which should leave me about 6 pounds wiggle room between the normal weight and underweight range) I have to say that this is the kind of thing that would have made me just hate everyone and end up on a binge. Hell and im used to being insulted and looked at like I have leprosy on a daily basis from most people I meet, it wouldn't spur me on it would have just have made it harder.
These people dont know how hard it is to loose weight. Its not one choice, you dont just wake up one day and say "hey im going to become fat. Wooooo! Bring on all the cakes!", its not something you can be bullied into loosing weight is a lifestyle change not a one off quick fix magical pill of leanness that we all should take to fit in with what society deems the beautiful people that we should all worship and love like they are some paragon saint of some holy order. No its a load of little choices and little things that you incorporate into your normal life, and it takes years of constant struggle to achieve. Yes its a struggle, after years of eating whatever you want its difficult to stop, ill freely admit food is addicting, especially when it seems everything is against you (dont get me started on the media, you cant watch tv for ten minutes without seeing some sort of calorie laden snack advert claiming its the next best thing since sliced bread). As much as it pains me to admit I was fat because honestly to me it felt like food was the only good thing left in my life now do they really think insults would help someone like that? Or would it just exacerbate the problem and add to the long list of things that are going against your goals.
If they really wanted to help people they would try and change the whole misinformation and downright dangerous practices the diet industry, instead of you know insulting random strangers who are either already trying to loose weight, or are just not in the right mindset to start. But hey I guess they wouldn't get that nice feeling of superiority they get because they are one of the special people, and god forbid they try and help people it would reduce their specialness after all.
Sorry for the rant and if it doesnt make sence, its early morning and im just spit-balling thoughts here.