Oh, it's not that. To me, the issue is Rowling's position. I won't go as far as to say she's being intellectually dishonest. It does seem to me, however, that she's disingenuous about certain aspects of it.
I'm not the meanie, she is. I mean, c'mon, she hurt Ursula Le Guin's feelings.
Seriously. Even Shakespeare's works have their sources. It's not necessarily about being original in ideas/structures/themes; it's about being original in presentation. Although I haven't read them yet, Rowling's works are great in that they have infused a new passion for reading in both children and adults—and at a time of instant electronic flashy entertainment. Furthermore, she's lit up the fantasy genre unlike anything seen since Tolkien.