I understand your position here, but I still have to disagree. You smuggled in a value-laden concept in the second paragraph: "unhealthy."

"Due to your knowledge of the unhealthy consequences of ice-cream, this will likely reduce your valuation of the good."

"Knowledge of the unhealthy"

=

Knowledge of a negative

Without objective value, what differentiates health and unhealth?

Perhaps by "knowledge" you are referring to a mere opinion or preference, but it sounds like you don't mean that. It sounds like you are talking about knowledge of an objective fact.