Disgusting says something about my emotional reaction.
Assuming that "sanctity" is a proper moral category then "unnatural" and "degrading" are objective as measured by necessary moral reasoning. So the fact that I am disgusted by something that is unnatural tells a third person that I have the proper moral sentiments to engage in correct moral reasoning.
This goes back to the teaching of Plato. If you cannot love that which is lovely, loath that which is loathsome, and despise that which is despicable, then you will never make any advancement in the area of moral reason. That lack of sensitivity would render you completely blind to the domain of morality.
