This seems like a very misleading comparison, having said that:
The real problem with how overweight people are treated isn't that people think "they need to lose weight", that's reasonable. Rather, society currently encourages hypocritical attitudes towards weight and generally seems to encourage giving fat people 'advice' in the form of ostracizing and treating them like shit.
People generally seem to consider being fat a special case where you're free to think and say whatever about the individual and enjoy lording yourself over them. Meanwhile, smoking, drinking, and plenty of other things that are commonly abused get a much freer pass from most people.
Added to that dismissive, simple-minded attitudes towards overweight people such as "stop eating six whoppers a day fatty" and many people who literally think anyone overweight is a bad person. We have those here on GAF. It's charming.
This is all actually counterproductive and doesn't really show one is concerned for overweight people, but rather just indulging in using them as, perhaps, the last major socially acceptable target to draw joy from their apparent suffering.
There are people who drink too much alcohol. Should we also not persecute these people with destructive habits?
In my experience people are far kinder and more supportive of someone who says "I drink too much", than someone who is even a little overweight. It's getting quite stupid, especially since it doesn't take authentic morbid obesity to trigger the response anymore. Perhaps it is a symptom of a narcissistic culture afraid of visibly displaying imperfection, but it's far less socially acceptable to be perceived as overweight by ANY standard, than it is to smoke, to drink. For a lot of people, even doing drugs.