First, it's easy to see why some (many?) are underwhelmed by NGLA at first playing; especially if there's little or no wind that day (which is often true on most mornings, BTW). You either love the 1st and 11th greens or you don't.
Second, one of the better observations of the National I've ever heard is, "the fairways may be wide, but if you hit a bad drive, it follows you all the way to the hole." Truer words were never spoken. At Pine Valley, it's obvious why that is so. Shinnecock, too (it's called uber-deep rough plus 1 water hazard). At National, it's equally true but not quite so obvious until you experience it yourself a few times and discover that a bad drive at National has REALLY left you with a problem. If this guy is a bomber, he probably made a few (or more than a few) double bogey's that, somehow, didn't seem like they should have happened. After all, those drives off the fairway didn't LOOK like they were in all that bad a place so what the hell happened? In terms of being "sneaky difficult", I would liken National to Merion West on steroids.
Third, I would encourage your pal to get his ass back to National for a couple of AFTERNOON rounds in a 2 club wind (which is the norm). He may not like it as much after that as he likes Shinnecock or Pine Valley, but if he still thinks it's a goat track, then there's something about the Golden Age that he just doesn't appreciate and probably never will. and tell him not to waste his $$$ on a trip to Dornoch, TOC, Muirfield, et al as he surely won't care much for those cow pastures, either.