If it was part of a transaction, it would be a part of the feedback for that transaction as communication is a key aspect of the transaction process.
If no transaction occurred because of said rude behavior, then I don't see where any feedback is warranted at all. (No transaction = No feedback)
If the behavior was threatening or against the site's rules, you could contact Admin (using the "Contact Us" link) to report the infraction and have him intervene, if necessary.
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 3/4/2024). I have added a large portion of my inventory to the site, and currently have trading turned on (details are in my profile).