Watching Fawn Hall and listening to the studied way in which she answered questions made it at once apparent that she had not only been coached in how to dress for the "show" but also exactly how to address the august body questioning her. For, she carefully used the term "sir" in the super-respectful manner of a Marine Corps member.
Since civilians in our egalitarian society rarely use this form of address in response to questioning, Hall gave the impression of super-honesty and super-earnestness. She answered the questions like a good little girl who only meant to do her best, sir.
The committee members would have been accused of harassing Hall if they had persisted (as they had, of course, with the males they questioned) in following through and zeroing in to the logical conclusions when Hall revealed the calculated illegalities of her activities.
It is not too far-fetched to visualize the extensive coaching of Hall by the Marine Corps member involved in this sordid affair: "Speak carefully and never forget to address the questioner as 'sir'. He won't know what to make of it, he'll need to rephrase his question, it will slow him down, and you'll be home free."
And so it proved to be.