The contrast is between the assailable public being and the protected internal one.
From the post-gazette.com
I'd solicit their stories, knowing that opinions are assailable but personal experience is not.
From the forbes.com
Humor goes a long way toward breaking barriers that are not assailable by logic and persistence.
From the kansas.com
What Potter and co. have also proved is that the unassailable Dark Knight is actually pretty assailable.
From the hecklerspray.com
These are both defensible-and assailable-positions.
From the economist.com
It was odd that this gentle-natured man, so easily assailable in general, should prove so unapproachable on the subject of personal expediency.
From the gutenberg.org
If it is Amazon's position that they will make available anything that is not demonstrably illegal, then they are only assailable on grounds of what constitutes good taste.
From the techcrunch.com
Everyone would assume and assess that without that assistance the Jazz would be hard-pressed to assert themselves, leaving them more assailable and less assured, we assume.
From the sltrib.com
If I make a passing statement that is assailable on grounds of its plausibility, lack of context, or novelty, but that I can support with a citation, then a citation is in order.
From the en.wikipedia.org
More examples
Not defended or capable of being defended; "an open city"; "open to attack"