Sure they do. Someone smoking or taking drugs gets yelled at all the time. Even just drinking too much will get you ostracized. Size is only a focus because obesity is related to diet, and a skinny person eating a piece of pizza, and an obese person eating an entire large pizza is not the same diet. The issue isn't someone who has 25 extra lbs on them, it's the person weighing 450+ taking up theater seats, airline seats, increasing healthcare costs for everyone, and other issues. Drug addicts increase crime and ruin the lives of more than just themselves, same with drunks that go driving around town.
It is possible to be a large athlete who exercises daily who is healthy or above average healthy. It is not possible for a couch potato who eats all day long and has a fatty heart and kidneys, spiking blood sugar and COPD to be healthy. Again, it isn't muscle weight that's the problem, its not a "few extra pounds", it's trying to say someone who weighs hundreds of pounds more than everyone around them that is the problem. They aren't out exercising and eating in a healthy fashion.
The fashion industry is heavily populated with people who have decided that 12 year old boys is the model of sexuality. It helps the look of clothing to have walking clothes hangers, and not someone built like a beach ball. Looking at porn you see much curvier women, not 12 year old boys (at least at legal web sites).
Another argument I've heard is it 'just looks bad'. This is easily disputed with the fact that many societies throughout history prized fatness.
Comparing human skeletons to morbidly obese is pretty much the same reaction from the majority of people. Comparing your average woman to the morbidly obese is not a comparison that's valid. You can look at the paintings from centuries ago showing some chubby girls, but in context you have to understand that these artists weren't doing graffiti. They were paid and commissioned by patrons to paint things, and when your subjects or commission asks you to do something you do it, or you don't get a patron. There wasn't a liberal NEA who was funding artists to do experimental work, nor were they documentaries.
There have been larger people have higher social status in some societies, because it showed that those people were "healthier" than the peasants scrounging in the mud and starving, and they could afford to eat like pigs. The attraction was resource based. There is zero comparison between being overweight compared to the starving in the past, and someone 450 pounds in a trailer park today.