It might not always be easy to tell a connoisseur from a bluffer, but if you are so bothered about it why not either - attempt to catch the person about. All very well decrying the person, as a fraud but connoisseurs can know the good years from the bad years, and have been known to swirl wine around their glass, look at wine lists etc.- accept that the person does know more about wine than you. Try this one. 'I'm terribly sorry, I'm quite ill-informed on this subject. It must be wonderful to know so much about wine, but it really isn't my hobby. Would you mind if I stick with the water?'Afterall is this really something to whine about? ;-) Looks like balderdash to me!