The vast majority of fat people should be ashamed of being fat.
Being fat isn't a lifelong handicap or illness like the body positivity "movement" wants it to seem, they just make it sound that way so they don't have to feel accountable for their own problems. It's much easier to cry victim and tell other people to stop exercising their thin privilege than it is to take some initiative and have some perseverance. Hard work is hard, so instead of climbing their way to the mountaintop they instead declare that where they are is the mountaintop and that anybody who tries to better themselves is just shaming them with thin privilege due to genetics and other factors beyond their control, when the biggest fucking factor is they need to stop stuffing their fat fucking face, drinking two liters of soda pop every day and go on a walk.
There are people with diseases that cause them to be obese through no fault of their own, but they are a very small number compared to the average American who is fat because they don't get enough exercise and consume way too many calories.
"Body positivity" and "Health at every size" is a joke. Obesity is not healthy, is 100% avoidable for most people and it should remain stigmatized, period.