There is a lot to agree with here, but also some to disagree with.

Granted that obesity often has a mental component to it, attributing responsibility is very important in addressing the problem.

For instance, people in abusive relationships are obviously in a rough spot and likely feel helpless, but it is the job of a therapist to give empathy as well as responsibility. It is typically far worse to take away responsibility.

With that said, assigning responsibility is something either someone close or qualified needs to do, and not up to people on the internet. We generally know nothing about a person and why they are the way they are. Someone who has lost a hundred pounds is still subject to the shaming.

Though the question "who would choose this body" seems like it makes sense, it isn't a valid argument. The choice is not between a fat body and a non-fat body, but rather between daily choices such as what to eat, how much to eat, and whether to go for a run. There are opportunity costs to everything, as well as side effects. We generally never choose negatives directly, but rather accumulate them overtime.

Lastly, obesity is a problem that tends to affect everyone, especially if you are living in an area with socialized healthcare. There is a societal cost to the problem. Same with smoking, not exercising, not getting your flu shots, and so on. Since these problems affect all of us non-directly, we have reason to reduce the problem, of course with full empathy. If the costs were totally on the person, that would be one thing, but when the costs are socialized, there is an incentive for people who are not affected directly to address it.