The purpose of "privacy" on a mailing list with hundreds of subscribers is
to avoid easy scrutiny and to bar participation from those who aren't an
approved member of the club. Note that affiliates can't simply add
subscribers; they have to request them. So the questions are - is a private
club concealed from public scrutiny a good idea? Is the opinion of those
who would answer "no" relevant or meaningful?
I'd answer "maybe, probably not" to the first and "apparently not"
to the
second. If they want to waste their time with another dead list with no
real purpose and few participants, let them. Few of the subscribers will
even share fluency in a common language. The likelihood of anything
controversial or negative coming from such a list is higher than if it were
public but still quite low.