The assumption that Rowling said anyone who disagreed with Hermione's casting was racist is incorrect. She was talking about a specific group of people":
“I had a bunch of racists telling me that because Hermione ‘turned white’ – that is, lost colour from her face after a shock – that she must be a white woman, which I have a great deal of difficulty with.
Thinking that only White people lose color from their face is weird because light skinned black people can do it too. That's purposely ignoring the wide range of skin colors black people can have.
So, yeah. The "Woe is me, I have been called racist" has to stop for actual dialog.
Since it would be extremely awkward and borderline racist for Harry to think of one of his dearest friends as “very brown” if her skin is naturally of a darker hue
Maybe she was light skinned and got darker. It's no more racist than saying a white person looked "very pale"
Hermione, as a white girl, tans
http://www.huffingtonpost.com/melissa-henderson/black-girls-tan-too_b_5575365.html
Indeed, if Hermione’s “bushy brown” hair is meant to be a shorthand for her being black, the message it sends is once again remarkably tone-deaf, since Hermione’s hair is described only as attractive when she spends hours straightening it into an unnatural position with special products before such a grand occasion as the Yule Ball.
Or, it could be alluding to the very real phenomenon where frizzy hair is considered attractive only when it is straightened because of beauty standards that may have developed unfairly. She does change it back.
By comparing Hermione to a panda, Rowling is clearly implying that Hermione has a black bruise around her eye surrounded by white skin. If Hermione is any color other than white, the comparison to a panda is poor imagery.
Black eyes can get really dark. If she was a light skinned black girl, a black eye wouldactually make her look like a Panda since Panda's have black around their eyes.
Even a cursory examination of the demographics of those listed as having the given name of Hermione on Wikipedia show that most of the notable people with the name Hermione are British and white. It would be unusual if Hermione were anything other than white based on the demographics of those who share her name
Most people named John or Peter are White. Would it be hard to believe that black people could have these names. The name Hermione itself was considered unusual when people first read it. Can't her parents have unusual naming conventions?
Whiteness is so fundamental to her identity
Nope.