I don't think that pointing out that there are many causes of obesity should make you angry. Would it make you angry if one pointed out that there are many social causes of teen pregnancy, even though abstinence works 100% of the time? Articles like this can be important, because they highlight that many things that we perceive as innocuous can be dangerous, although I agree that diet and exercise work without fail.
It is not the content of the article that I find frustrating but the context in which the article is framed. It reads as if we are already doing too much to tackle obesity through the promotion of a healthy lifestyle (diet and exercise) or attempting to overcome the associated social barriers. I think it is important that we understand all of the contributory factors, but let's not undermine the importance of what we already know.