2) "They're doing it because they believe that it works" implies a certain deliberateness and design. Having spoken with a few USMC recruiters back when I was a teenager, I'm very inclined to believe that they've put a lot of thought into this and that there is a fair amount written about how they use these harsh methods to solve the problems like "How do we give people from a wide range of social backgrounds the mental toughness to be able to do trigonometry in their heads while mortars are going off near them?"
This is quite different from refusing to deal with one employee who has a habit of randomly screaming at people about accounts receivable issues.