Again, Robert is talking from this weird "movie world" perspective he has.
Slight power-level here, but I was military for 1 year and a half (not american military, where I'm from once you turn 18 you get the chance to serve for a a short period to become a reserve and get a small salary, and I needed the money).
Anyway, during my stay, sure, the officers were firm, and if you screwed up bad you would get punished or at least some yells... but Robert seems to think the military operates like fucking Full Metal jacket, with psychos dressed up as Sargents. Not at all, everybody is a adult there, and you do the tasks that you are told to and that is it, none of that "you are the scum of the earth, pay me 50 push ups!!!!"
Obviously I don't know how it goes in the US military, but I think it would be safe to assume that they act like adults as well and not some Hollywood caricature.
As for Trump, first time hearing about his relationship with the secret service, but one thing everybody says about Trump is, that while his public image comes across as unsavory, when you are 1 on 1 with the man, he is quite charismatic and charming, and makes sure to know everybody on his staff by first name, so it is quite possible he was quite kind to his secret service agents.
Makes more sense than just assigning "Daddy issues" to highly trained professionals because that is what Robert saw on crappy, overrated war dramas movies.