Nolan wouldn't say that with those words. he knows that it would offend some fans.
But the fact is that if he can make Duacrd Ra's, if he can introduce a new character that's vital to the hero's story like Rachel, if he can have Two-Face's origin attached to the Joker and not Maroni and dying in the first film, he could have had Robin.
But he did not.
Nolan doesn't think Robin belongs to his take on Batman the same he has said Superman and Batman don't live in the same universe.
Also, Batman was ready to have a replacement (Harvey) in TDK, so if Nolan wanted Batman could have been ready to have an apprentice. 
If some of you can see Robin working in Nolan movies, okay, But Nolan doesn't.