My reading was more sympathetic than yours, dear Casca…
I felt the comment mean to draw attention to the fact that they are often exposed to the worst of human nature, see friends blown to smithereens, have to be on edge all the time when in certain dangerous duty assigments and that the human psyche is not well equipped to handle such things and can, simply, break.
Marion gets nod for funniest comment i have read here in the last week… came THAT close to blowing my morning coffee out my nostrils.