Concrete example: I worked on a wildland fire crew for a while as a young fella. I didn’t have the seniority to drive my water truck, and the driver who owned the truck was a very stupid man. I almost wound up dead at least once because of his decisions, but then he also would have been, so this story doesn’t fully relate to your father’s wise aphorism. 
Didn’t go back to that crew after that tour, even though it was the most satisfying and best paying job available to me at the time. 

 His insight came from years in the oil industry. Specifically, the accidents that happened on rig platforms. Almost always caused by morons and it was the good people who got seriously injured or worse. 

 Dangerous jobs and morons seem to attract one another. Such a bad combo.