I agree about BMI often being a bad measurement. Even my own doctors ignore it on me because my BMI is well into the obese range and yet every other measurement of health is in the healthy range, most well into it. My body fat for instance is just below 30%, which is perfectly healthy for a woman. My waist line is well into healthy range as well. Additionally, all my tests such as blood tests come back more than healthy and show that I'm not at risk for any obesity related conditions. Of course, I don't look like the standard "healthy" body most people imagine a woman should have. I would look fat to anyone who doesn't know the full picture.
That's why I always hated that whole thing people say that "If you're BMI is high and you're still healthy it'll be really obvious." People just assume that high BMI and healthy means muscular, when you can have a normal body fat percentage as well as other measurements but still have a high BMI.
This is even ignoring the fact that even when you are genuinely obese and unhealthy, it often stems from body image issues in the first place. The same way a depressed person often goes "I'm doing everything wrong anyway so why bother even trying?" A fat person often is having the struggle of "I'm ugly anyway so why even bother trying to be pretty and healthy? Healthy just means I gotta live longer being ugly." That's why berating people for being fat usually doesn't work. It just makes them feel worse and reinforces that idea they already have that they're too ugly to bother. Sure, some people it might kick into gear to try their best to lose weight to prove they're not ugly, but that's the difference between somebody who still has hope and somebody that's already lost it all.