SE does indeed do something against people harassing someone else. The problem is that many people getting into trouble with "bullying" people simply fight back. How should an GM handle that situation? Ban both? I wouldn't go that far to even call this bullying.

The other story are the ones really being bashed on by an individual without doing anything back. But blacklisting these helps for most problems, just leaving the MPK issue and the rumors such a person could spread. I personally haven't heard of any MPK bully in my entire time in XIV, but that is some issue GMs surely can help with.

About spreading rumors: That is some serious problem and the only ones who can change it is the entire playerbase. Don't judge people by questionable information of other players - make yourself an own picture! That player might be a LS mate or even more to you, but in many cases it still is just a person from the internet you don't know. By questioning things others say you're taking a bullys greatest power.