That's gross and wrong: Disgust in morality

The case of Armin Meiwes

Armin Miewes is infamous for killing and eating Bernd Brandes, who volunteered for the act with full knowledge of what Miewes wanted to do. Despite Brandes giving consent, Miewes was ultimately convicted of murder, and the disturbing nature of the case raised considerable legal and ethical debates about the limits of what is acceptable for people to do.

In Moral Foundations Theory, as described in Jonathan Haidt's The Righteous Mind, there are several foundations which form the basis of different moral beliefs across the world. One of these foundations is Purity, also called Sanctity/Degradation, which is described thusly:
"This foundation was shaped by the psychology of disgust and contamination. It underlies notions of striving to live in an elevated, less carnal, more noble, and more 'natural' way (often present in religious narratives). This foundation underlies the widespread idea that the body is a temple that can be desecrated by immoral activities and contaminants (an idea not unique to religious traditions). It underlies the virtues of self-discipline, self-improvement, naturalness, and spirituality."

"The Sanctity/degradation foundation evolved initially in response to the adaptive challenge of the omnivore’s dilemma, and then to the broader challenge of living in a world of pathogens and parasites. It includes the behavioral immune system, which can make us wary of a diverse array of symbolic objects and threats. It makes it possible for people to invest objects with irrational and extreme values—both positive and negative—which are important for binding groups together."

Questions:
1. At what point does something become so disgusting that we consider it morally wrong? Is there any logical way to tease out our boundaries around this, or is it just vibes?

2. We live in a world where we are increasingly exposed to things that might have been considered shocking and revolting to previous generations; how does this affect our perception of what is right or wrong? Can exposure make us more accepting and sympathetic, or is it a corrupting influence?

3. How important is it to be able to give rational justifications for our moral beliefs? Why might it be beneficial or unnecessary?

4. If someone you were close to died naturally and their last wish was that their body be eaten by their friends and family, assuming that you know their body is not going to make you physically ill, would you be willing to help fulfill their request?