Frogglestew
So no I wouldn't be as harsh as you're envisioning and its probably because of my terrible wording in my previous post, but what I will say is fat shaming is only going to hurt someones feelings, but fat acceptance will kill them. IF someone is fat you shouldn't say oh you're disgusting but rather say you're overweight/fat and need to make life changes quickly. Even if you put it nicely they might still view it as fat shaming because they dont want to hear the truth.
Those are my views, they might conflict with yours.
i agree with you here. if you know the person as a friend it's perfectly fine to say 'hey i'm concerned for your health man'. it happens all the time and can be good for the unhealthy person.
but
Frogglestewverbal flogging
is different from a polite/constructive conversation. especially if you don't know the person as a friend and are just talking to someone through the internet. remember there is a real person behind the screen.