Originally Posted by Wikipedia: Disgust: Disgust and Morality
Although disgust was first thought to be a motivation for humans to only physical contaminants, it has since been expanded to apply to moral and social moral contaminants as well. The similarities between these types of disgust can especially be seen in the way people react to the contaminants. For example, if someone stumbles upon a pool of vomit, he/she will do whatever possible to put as much distance between himself/herself and the vomit as possible, which can include pinching the nose, closing the eyes, or running away. Similarly, when a group experiences someone who cheats, murders, or rapes another member of the group, its reaction is to shun or expel that person from the group.[37]
Jones & Fitness (2008)[37] coined the term "moral hypervigilance" to describe the phenomenon that individuals who are prone to physical disgust will also be prone to moral disgust. The link between physical disgust and moral disgust in the United States can especially be seen in the fact that our culture often refers to criminals as "slime" and criminal activity as "stinking" or being "fishy". Furthermore, people often try to block out the stimuli of morally repulsive images in much the same way that they would block out the stimuli of a physically repulsive image. When people see an image of rape or murder, they often turn their heads away to inhibit the incoming visual stimuli from the photograph just like they would if they saw a decomposing body.
Horberg et al. found that disgust plays a crucial role in the development and intensification of moral judgments of purity.[38] In other words, the feeling of disgust is often associated with a feeling that some image of what is pure has been violated. For example, a vegetarian might feel disgust after seeing another person eating meat because he/she has a view of vegetarianism as the pure state-of-being. When this state-of-being is violated, the vegetarian feels disgust.