I read that Slate article. The author WAY overstates his case. If obesity were simply a matter of genetics, as he implies (writing "How fat you are has a lot more to do with your genes than with your behavior. As much as 80 percent of the variation in human body weight can be explained by differences in our DNA."), then the per capita number of obese people should be the same county to country, or through time. In actuality, the percentage of obese Americans has doubled since the early 1960s. The "caloric environment" (wide availability of high calorie, cheap food) obviously affects people's behavior. Due to genetic factors, it affects some people more than others.
I agree that people aren't necessarily to blame for their natural reactions to this situation, but it's disingenuous to claim that there is nothing that these people can do. There is some number of people who are obese today that wouldn't have been 50 years ago. If they can contrive, however difficult it may be, to eat and live as though it were 50 years ago, they would not be obese. Being hateful is not in order, but neither should we shrug our shoulders and pretend like there's no problem or that there's nothing that an obese person can unilaterally do to lose weight. In the end, unless we really want to contemplate pervasively regulating what food people can eat, the solution is going to have to come about from changes in people's behavior.