Fairchij: When confronted by a person who is persistent in Private Messaging who makes insulting remarks what is the correct process for dealing with that person from an Agoracom rule perspective?

Formally and without having seen the PMs you received, I would suggest one or more of Agoracom Rules 1, 2 and 5 apply.

The Agoracom Six Rules of Use are not restricted to public posts, but explicitly apply to "the AGORACOM website, which includes, but is not limited to, blogs, discussion forums, stock hubs, "private messaging" system, and any other electronic medium used for communication with others on AGORACOM".

So banning is absolutely okay.