Are some jobs morally and psychologically hazardous?

My first job out of college was working for a DRG decoder, meaning that we'd correct the Medicare codes applied by doctors' offices in order to increase the amount the government would pay out. Although our company was mostly honest, I felt there was a moral hazard in the temptation to not just nudge the code toward a more profitable diagnosis, but to outright lie. Also, even though we were helping doctors overcome the burden placed on them by government, it always felt "unclean," living as it were in the belly of the beast. More broadly, it seems there are certain jobs that — although perfectly appropriate under the circumstances — bear special moral and psychological hazards. The police, the military, psychologists, lawyers, all are by definition working only with the "darker side" of life. (No one calls a cop because they're having a wonderful family moment.) Are there certain jobs that inherently carry extra moral and/or psychological baggage? If so, what are those hazards are and how can a person best to minimize them?