Harmful for the same reason as the 'healthy at any size' campaign, and anti progressive because if they claim health at every size, then they deny there's a huge malnutrition problem in America. It would be solving the problem of food deserts and obesity by just saying 'no no these people are actually healthy' instead of making sure they don't live in a fucking food desert.
The campaign that advocated for healthier activity for all people with a focus on positive reinforcement, and had it's message willfully misinterpreted by reactionaries?
Healthy at any size doesn't mean you're healthy at any weight, no matter what. It means that no matter your weight, you can still engage in healthy habits. There's discussion to be had about structural changes to be made in America about how food is produced, advertised, and sold, but engaging weight issues on a positive level is only helpful for everyone.
Huh. I never knew that.
There was a very deliberate effort to push the idea that HAES meant being overweight was healthy by reactionaries, to the point where the misinterpretation and the overblown reaction to that actually happened overshadowed the actual ideals of the modern movement. Anyone on reddit a few years back might recall /r/fatpeoplehate and /r/fatpeoplestories. From https://www.nationaleatingdisorders.org/size-diversity-health-every-size:
"The basic premise of health at every size, as written in [Lindo] Bacon’s Book, Health at Every Size: The surprising truth about your weight, is that 'Health at Every Size'(HAES) acknowledges that well-being and healthy habits are more important than any number on the scale.
The way informationated is disseminated these days is troubling. It's not like there was ever some golden age of truth, but social media and the internet in general has really amplified the way misinformation spreads.