I guess it depends. ... I was morbidly obese by the time I was 16 years old.... my doctor told my parents I was anorexic and to force feed me as a child... well I got used to eating way to much and my parents never put their foot down.
After I lost 120 lbs I vowed to never get fat again. Fast forward 5 years, got married, wife was pregnant and fought some health and addiction issues, and I gained the weight back. It was a crushing failure. But again, ive lost 100 lbs a second time and ill be damned if im going to do it 3x. But this timw has been much more successfuly because im doing it properly.
regardless..... I agree that its their failure if they get fat, especially as an adult when they should know better. But 99% of people have no clue about diet or exercise.