I thought of that, but wouldn't the taster have a predisposition to look for flaws in the beer? My thought was you have 1 flAwed beer (theirs) and one flawless beer (snpa), and it would be a bit more 'blind'. How would you construct the tasting?
What they really need is sensory analysis training to learn what the flaws taste like. It's true that many people will like some flaws - the raisiny/sherry flavor of oxidation, nice buttery diacetyl, appley acetylaldehyde - these are not all bad flavors, they just don't belong in beer. Most people don't recognize that.
Being self-critical is a rare and useful skill. I'm not too shocked at their response, but they were lucky to have someone bring it too them. Most future reviews will be on BeerAdvocate, Yelp, etc. Unfortunately, they can probably survive on uninformed customers - but they won't thrive.