Sometimes major dramas will occur, such as an all-out war between subscribers, a person who repeatedly posts offensive material, etc. The only way to deal with such incidents is to make sure you have your "benevolent dictator" hat firmly on your head, and sort it out as quickly as possible.
Suitable ways of dealing with such problems include warning the perpetrators that they will be banned from the list if their activities continue, and/or actually banning them. There's not much else at your disposal.