Federer just didn't like young Djokovic. He has never been disparaging towards youngsters in general. He has grown more respectful to Djokovic after he matured.
It was a bad call from Federer, to make comments like that. I'm sure he didn't like Novak, partly because of his retirements and partly because he saw that Nole was not afraid of him, or in awe of him like most players on the tour. But it's true that Novak has earned Roger's respect with time.
I appreciated Roger's comments to Novak after the WTF final very much. He said: "Congratulations, Novak, you're the best...I can't play much better than I did today".
That's amazingly gracious after such a painful defeat, and I know I'm not the only Nole fan who has a new-found respect for Roger after he said those words.