There's no way we're reading the same thread. At least, we're not perceiving it the same way. A huge amount of the posts on this thread go like this: "Be fat if you want but it's unhealthy and you'll die!" Can you imagine being a fat person and seeing that?
EDIT: Also, if you agree that it's costly to be skinny, then logically shouldn't everyone lay off fat people and stop demanding they fix their problems?
personally, I've perceived a majority of the responses more light-heartedly, however what they have in common is the belief that being fat relies on the person's personal choices, whereas in reality, that's not always the case.
I think what everyone is trying to say - at least, if my perception serves me correctly - is that they would not judge someone for their size, nor do they encourage people of such size to feel shame for their body, but do believe that obesity is a common and important health issue that can lead to further issues, and that it's important that if someone CAN reduce these risks that they do, purely out of concern and not to pick on fat people.
Therefore, I think that these people are not being rude, but while accepting fat people, they also acknowledge that it is an issue and it shouldn't be promoted or celebrated, but acceptance of it should.
Then again, it probably is impossible to contribute to this thread without someone taking it the wrong way, and while I disagree, I can see why you'd be offended, and really hope that these comments don't make you feel bad! have a nice day c:
EDIT: this is referring to morbid obesity, being generally overweight is hardly an issue.