I think it means that humans can learn to suppress their natural instinct of disgust, if they know the disgust is not necessary. So it isn't really counter productive. E.g. that example they gave of cancer patients.
But I don't really agree with that. I think disgust is ALSO something you learn from your environment. For example, I wonder what the reaction a baby/toddler would have to those two towels. People who eat tarantulas do not think it is disgusting, perhaps because they learnt from their environment that it is not disgusting. So I don't think they suppressed their disgust, as it's something they never had in the first place!
But hey, what would I know on the matter. They are the scientists so they must be right
