Actually, the best way to confront this character is not to act smart, but act surreal. The reason I say that is because this character will eventually give up thinking that you, floater, have truly gone mad. Another way to deal with this is to speak in an entirely different language all together! I suggest you speak in an invented language, a language that cannot be understood by anyone but yourself.
This will prove successful, and the perpetrator will eventually give up trying to insult you and your site. He will be left clueless and his ideas will diminish. He will not fully understand why you are speaking in an unknown language. I recommend you use this unknown language to ask him questions such as:
[Example] "Aga ga balababa iya iggy pop?" (No such translation exists)
His reply will most likely be somewhat of a confused nature.
Keep asking him these strange questions in this style of invented 'Iggy Pop' language. He will soon lose interest and find someone else to bother.