There is a reason to that (and I mean a collective reason, not anything specific to him). A Federer fan who cannot stand Nadal, in general, out of selective memory, remember just the parts about Nadal's game that bothers him the most, and that is precisely the relentless defense. So this (hypothetical) fan is sure Nadal's game is one dimensional -- after all, that's the only dimension he is paying attention to. The details that makes this formula particularly damaging is that, obviously, the defensive game is the last resort Nadal has, after all, everyone has bad days and bad patches. So when we see Nadal playing his C- game and still winning, this fan will say "see, that's the only way this guy can play".
Every great player needs some last resort to cling to. Federer has his serve -- and, not surprisingly, the Federer haters say he is all about the serve. It is not a perfect parallel, but still has some truth in it.
Maybe, if we would have the time to look in detail, we would find that what makes a great player "great" is precisely not how well he can play while on his peak, but how effectively he can survive while playing like shit. Each one in his own way, Fedal are masters on this, and on this particular front, specially on clay, Nadal is ahead of Federer.
