There is much more to being obese than just eating and not exercising, though you are correct in saying that better diet and getting off your arse is the best remedy. But I think this applies to much less than 99% of the population.
However, other physical factors come into play. Reduced metabolism, under active thyroid gland, digestive disorders, and a possible 'fat gene' also have an effect.
I have two friends who both weigh over 20 stone. Both eat less than I do and go to the gym. Yet I weigh half of what they do, don't count calories and don't go to the gym (but I am always active physically). They get frustrated that I can pig out and not put on weight, whereas they only have to look at a cake and they pile on the pounds.
Also worth bearing in mind that both were of average build up to their 40's, then suddenly the pounds started piling on yet there was no change in their diet.
Why is this? Why can I eat pretty much what I want and not put on weight? Why are their bodies so susceptable to weight gain compare with mine? Who knows, but it does go to show that there is more to being obese than simply over eating and not exercising (though I do agree that in many cases that is the primary problem).
The saddest thing though, is that my friends get labelled as 'fat slobs', 'lazy', 'greedy pigs', 'disgusting' etc. purely based on their physical appearance. If those aiming those comments at them could see how much they are trying to lose weight and how hurtful those comments are, perhaps they would take a different view. They are still human beings, and have emotions like all of us. Not all fat people should be stereotyped, which is what so many people wrongly do...