[bryant]

People grew up making fun of others for being overweight. Suddenly a medication making it treatable (and possibly providing an explanation for why the prevalence of obesity skyrockets in developed countries) validates the idea that it's a medical condition.

Relatedly: it validates that people are assholes for making fun of others who are overweight. And not many people like feeling like an asshole.

Edit: starlevel004 is right.

[Starlevel004]

Correction: Lots of people like feeling like an asshole. They don't like being called out for it or being wrong.