I'd say getting PTSD and depression working in a slaughterhouse, or dealing with death as a healthcare worker only proves the point? It's a correct sane reaction.
I'd agree there. I personally interepreted the "some people aren't squeamish" comment to imply that the people in these professions are immune from negative psychological consequences of being those professions.
Can't speak to the others.
https://pmc.ncbi.nlm.nih.gov/articles/PMC10009492/ - slaughterhouse workers
https://pmc.ncbi.nlm.nih.gov/articles/PMC12174799/ - healthcare workers