I think most people here are misinterpreting Gladwell's tainted supplement argument. He isn't suggesting that as the likely reason for a positive test, he's simply stating there are other plausible ways for her to have tested positive.
The concept here is no different than any other "crime" that's been committed, it's a combination of physical evidence and a narrative that determine a desired outcome, whether that's to convict or to defend. Example, there's a dead body, a gun with ballistics matched bullet that was found in the victim, and your fingerprints on the gun... did you murder someone or did you protect yourself? The story matters.
I don't think he's supporting her innocence, I think he's simply suggesting the exact title of the article... it's unsatisfying because we'll never get the story... guilty or not. Bummer.