List server control should only be used in two situations. As Nimrod said, if it is illegal to list a server because of its name, the server should have its name changed or should be delisted. Repeat offenders could be banned from listing servers, but only after reasonably being requested to stop.

If someone is purposely performing any kind of denial of service attack on the list server, or any other malicious activity directed toward the list server, they should be asked to stop, and if they don't, they should be banned. It is up to the operator to decide what constitutes malicious activity, but it should be reasonable.

Activity within games is entirely the responsibilities of the game hosts and clients (and to some extent their internet service providers). The list server operator should not take action for anything that happens within games, unless it is somehow causing problems for the list server.