Some people are terrified of being treated like adults. I've chatted to quite a few fat acceptance/rights/whatever people over the years, and most of them really do agree with you and are trying to lose weight - they're mainly just trying to stop fat-based bullying, or ask clothing manufacturers to make stuff in their size, which I think is totally fair enough: are they supposed to walk around naked until they're small enough to fit into the current-max clothing? I'm not trying to put words in your mouth and claim that you're against them, and this, mind you.

But I too have encountered the archetypal fat-acceptance supporter who claims that obesity has zero effect on health. There aren't many around, but they do exist. And yup, it's a ridiculous stance. I too was once overweight, and I sense they're doing what I once did: try to avoid admitting to myself I'd taken poor care of my body, and lash out, and make the nasty adulthood and competence go away. I wish I could phrase this more tactfully without removing the competence-bit, but I don't want to stop treating them like adults.