You need to have the stomach to do some jobs. I remember the time when many of my friends in the medical school asked me to go with them to the dissection lab in the first year of college; I was doing CS at that time, but the professors did not know the students yet, so they gave me a lab coat and went with the group. 10 minutes later, a few students fainted, some were puking in the corners, the professor asked me to put the liver in the body on the table because I looked the least affected. I did it, so he asked me for the name to give one extra point at the exam for the semester (I gave a friend's name that was puking).

Most of these people grew up in cities, I grew up in the country side cutting chicken or pigs for food; this makes you less sensitive to some extent.

My friends that are now MDs told me that year was the worst experience of their lives. Being a Facebook moderator can be worse than that, so it can be really bad for some of the people doing this job.