I reckon there's special pleading going on with the obese. Way more anger & snottiness gets directed at them (at least on the parts of the Internet I see) than at, say, smokers, even though smoking is at least as bad in every relevant way I can think of.

(Here're some obvious examples. At an individual level, smoking is associated with shorter life at least as much as obesity. At a global level, smoking kills more and reduces DALYs far more than high BMI. Like obesity, smoking is associated with lower IQ & lower conscientiousness. And so on.)