People constantly compare obesity to smoking and drug addictions, which is why we shouldn't 'allow' people to be obese by asking people to accept that their beauty isn't defined by their size.
Obese people are constantly harassed, and called 'lazy' and 'worthless' because they can't lose the weight, but what people forget is that obesity is often a result of a food addiction - although food isn't physiologically addicting, it is psychologically, which is a fair amount of the reason why people can't give up smoking or drugs - it's an emotional crutch. So when you call someone lazy and not worth loving because they eat too much and exercise too little, all you're doing is feeding their hunger, as a large majority of people find comfort in food.
Also, despite the vehement defence that "we don't encourage smoking, so why should we 'encourage' obesity", equally, we don't walk up to people in the street who are smoking, and call them lazy and a drain on everyone else's resources, or tell them that they're killing children in Africa because they're not donating the money spent on cigarettes to charity, and we don't tell them they're not worth loving because of their nicotine addiction. If we don't do that to people who smoke, what makes you think obese people deserve it?
If you don't know someone, you have no idea of the situation behind their obesity - it may be due to grief, depression, a medical disorder, too little time to exercise or eat properly or simply a bad education on healthy eating.
So surely a better way to deal with the obesity crisis is to educate parents and children, adults and teachers to eat healthily and exercise regularly, and motivate people to help them lose weight through encouragement, rather than telling them that their worth is inversely proportional to the size of their body cells!
tl;dr, don't verbally abuse people about something that is none of your business