The 'fat abuse' kind of prepared me for being heckled for being trans. Something which happens rather more frequently, these days. I've been this body shape since around 5 years old (stayed with grandparents for a while, and my grandmother didn't think I was happy unless I was eating.) So yes, I've grown up with the ridicule of my peers, rather than just strangers, and like to think I have a thicker skin as a result. One memory of primary school is regularly 'forgetting' my swimwear on swimming days, so that I didn't have to change in front of others. Children are, of course, pack animals (and schools allowed them to be, back then.) They pick on the different, be it body shape, race, or anything else that makes someone stand out from the crowd.
I now find myself in a situation where I've always considered myself massively overweight, and yet (based on the 2018 UK stats) if I were 2 inches taller, I'd be average BMI for my age group. (We are, of course, overweight as a nation.) School reunions are an eye opener, because I'm far from the fattest one there. I've also aged better than most.
People who haven't suffered from a serious addiction underestimate what a crutch these substances become. When you've watched a chronic alcoholic, who's been hospitalised with liver failure twice, respond to the news that they've mashed their liver up so badly that continuing to drink will kill them, by going on a drinking binge, you start to understand the smokers outside of the hospital. Whatever's put them in there (which might not even be smoking related) is likely causing them stress, and they need their crutch right now. And like Steve McCroskey in Airplane, that probably isn't the right time to quit anything (mentally, at least.)
There is, of course, nothing wrong with encouraging people to live healthier lifestyles, and applauding them when they do. It's just that Joe Public doesn't seem to know the difference between encouragement and shaming, and tends to use negativity as an enforcement tool. Yet when you make someone who comfort eats miserable, what do they do? Generally speaking, they go straight to the fridge. Fat shaming is actively counterproductive.