I hear ya.
It's something that gets me very angry. To the "fat acceptance" movement, anyone who is naturally slim OR has worked for their body (be it muscular, slim or so on) is oppressing them and is unfairly privileged over them. Just look up "fat acceptance" or "thin privilege"
To them, being obese is healthy and they think the world should accept that. The amount of amazing, over the top lies they tell themselves is insane. They will sometimes put pictures of themselves, usually obese but doing basic yoga moves.. Congratulations, just because you can get into a yoga pose doesn't mean that your body isn't swimming in fat.