Well, I don't think you can complain that other folks failed to display independence in tricky circumstances, if merely being employed provides sufficient persuasion to define your path. In taking the job, you accept the responsibilities of the office. If you don't want the obligations, avoid the job - or quit the one you have if needs be.
He has written a book about dereliction of duty. That doesn't make him a modern day philosopher, in my view. It's one of those things more easily said in hindsight or written in a book than done in real time.
Who were the refuseniks when Dubya decided to torture terrorists? Where was McMaster?
I will wait and see. He may be good. I dunno. But just because he wrote his book and a few senators are supportive doesn't tell me enough to have an opinion. How folks deal with complicated loyalties is a subject with a long record. Ask Judas. Or Brutus. Or Thomas a Becket. Or Thomas More. Or Von Stauffenberg. Or Snowden. It doesn't necessarily end well for those in a privileged and trusted position who have independent moral convictions and - precisely because of them - act.
Principled dereliction is usually called treachery in real time. Hard path. Disloyalty is not usually seen as a virtue. You put on golden manacles when you accept the job. You only find out about the strength of your morals/beliefs when they are on. Are you ready for your own destruction, because that is what lies ahead? Have you the courage to make that choice in favour of your convictions? This is the question. It is much easier to theorise about how you ought to act than actually to do so.