The recent Nautilus article about why our brain hates other people[1] makes an attempt at categorizing how we view people along two axis. How emotionally warm we perceive members of another group and how competent we perceive them. The article than goes on to describe how we react to these categorizations. According to the article we are physically disgusted by people with both perceived low competence and low warmth. The effect is compared to seeing a maggot infected wound. The article uses drug addicts as the example of a group we perceive that way.

[1]http://nautil.us/issue/49/the-absurd/why-your-brain-hates-ot...