I think his friend who called him a liar is really to blame. Just like David said, it's like walking up to someone and saying, "JAPAN." There is no way to lie with a single word with no preceding context.
Or perhaps his friend was also being sarcastic and he just missed it. In Cret's defense though (amidst all this blatant flaming :p), I also find sarcasm a difficult thing to convey and perceive via IM:
http://www.bigblueball.com/forums/in...m-over-im.html