It's a tricky question. I think part of it is how tricky it is to define what 'obese' is - take two people of the same height, age and gender, for example. One person may be perfectly healthy at 20 kg over the 'normal' weight (a term which is a slippery slope at best), while the other may be perfectly helathy at 20 kg under the 'normal' weight. There's a difference between being medically obese and being visually very 'fat'. You can be thin as a rail and yet have cholesterol that would kill a horse, or be visibly overweight and live to be 100 with nary a hint of diabetes or heart disease.
At the same time, I have to say that if your omentum is so loaded with lipid that you have a stomach that hides your knees, or you are so morbidly obese that you cannot sit up unassisted, then you need to seek medical help if you are able - regardless whether your condition is a result of a genetic condition or poor lifestyle choices. There is a point at which you *should* lose weight, for the sake of your life. At that point, there is no use people saying 'oh, you're not too big, you don't need to lose any weight' - that is a cruelty, not a kindness. They need to offer help and support, to enable you to safely reach a weight at which you can have a normal life expectancy.
Everyone has a weight at which they are healthy. Heavier than 70kg is *not* fat, unless perhaps you are only like 10 years old, in which case you *probably* need to look at getting some help. It all depends on age, height, body chemistry and genetics.
As for dealing with the 'obesity epidemic', I think the main focus should be on children, as they are the ones developing a type of diabetes that they should never have to worry about, the ones who are having their lives shortened and made painfully difficult. Essentially, I believe it is the parents' responsibility to provide their kids with fresh, nutritious food, teach them about looking after their health, and introduce the concept of moderation when it comes to sweets/McDonalds etc. Kids parties should be the orgies of cake and ice cream and chips and fizzy drinks. Not the average meal.
Wow, sorry for the wall-of-text people...it's such a complex issue it's difficult to sum up a view in a few words...