Yeah, I re-read what I wrote and it comes off a bit furious. The thing I see as an "illness" is the fats inability to control their relationship with food. Top that with the wilful ignorance you stated, you have a mix of stuff going on. But if I start thinking about what constitutes mental illness I dive down some deep rabbit hole.  I don't think that fats are body positivity activists either, they just use the label.