> Their obesity exacts great cost to the medical system that we all have to bear, it takes from their productivity that they could offer to others (society and their own family) and benefit from themselves in a multitude of ways.
This complaint runs into a more fundamental dispute: freedom versus collectivism. In a purely libertarian world, everyone would be absolutely free to do whatever they want. In a completely socialist world, one is only free to do what they want insofar as it has no negative effect on others, or if it does, they should compensate others for the harm they cause.
There are problems with both extremes. Absolute freedom can lead to anarchy which will effectively prevent people from coordinating and building anything collectively. But forcing individuals to adhere to a strict cost/benefit analysis for every action stymies creativity and personal freedoms.
When considering a ban on a particular individual behavior (e.g., eating too much), it's perfectly reasonable to talk about the larger social harms (e.g., increased medical costs). But it's also important to consider the freedoms that are being taken away by such a policy (e.g., the freedom to eat what you want).
Western society has never solely been focused on maximizing overall social well-being, it has also balanced ideals of individual freedom with it. China, in contrast, has focused almost entirely on collective well-being over individual freedom. Many people (myself included), would prefer to live in a less successful but free country rather than a more successful authoritarian one.