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.