That's exactly the tautology: "Moderation" is "the amount that is good for you." So there are no exceptions to "moderation is good for you." How else would you define "moderation" in this context without a reference to the amount of something that is beneficial? It's not as if "moderate" is an amount that exists out of context that can be applied to both donuts and broccoli without knowing which one of those is good for you.
Edit:
Also there isn't really a healthy amount of doughnuts you can eat, so by your definition, a moderate amount would be zero. Which isn't really what the 'everything in moderation' rule means.
