I agree they should. As someone else posted, they should enforce noise and disruptiveness, not age. If the mere presence of a child is bothersome to someone, then NCL is simply not the right cruise line for that person. NCL is a family cruise line so children are to be expected.
I have indeed been there. If you re-read my comment you will see that it was not an original though, it was in reply at this person, whom I quoted in my comment: