This is a really thoughtful comment, thank you. I agree with everything you've said with one exception, and I appreciate the additional context I didn't know about.
I would say that it is very reasonable to argue that "...they are so distant from anything that might actually remotely justify the action...", but that does not imply that "...there is a very good reason they aren’t highlighted..." is the actual reason Ni'ihau isn't highlighted. I'm still pretty convinced it's because it's inconvenient, awkward, uncomfortable...not because those events and the context they were part of made a bad justification for trampling the rights of 125,000 people.
As I think about it more, the thing I'm stuck on is more like...Ni'ihau and the stuff you mention, and the context that makes for, all make the people involved seem more reasonable, less kind of...crazily racist and afraid...a little less cartoonishly evil. And a lot of people these days don't like that. They want an "other", an enemy that is simple and easy to hate. Clear right and wrong. Red and Blue, D and R, Tory and Labour. And I think that's childish and wrong and bad in almost all circumstances. Pointing out Ni'ihau amidst the self-flagellation about Japanese internment in WWII makes that sort of person look at something he doesn't want to look at, but that he looks at it is good for him and for the rest of us.