One should be able to bring this to the attention of the particular user group as a violation of posting.
My buddy moderates several FB groups and is constantly booting people off that violate FB rules.
As mentioned some may not do such a good job, but all you can do is report it and sit back. WIth enuf violations unanswered, I believe that FB will remove the group!
He's due in for a visit in a couple of days. I can broach this subject with him and perhaps bring some better experience to this post!
Steve