Why?...she says why...she disapproves of him as a person.
Hemingway?! He was an abusive alcoholic misogynist who squandered half his life hanging around Picasso trying to nail his leftovers.
As for racism, the teacher doesn't actually accuse her of that; it's more about the fact that, in his eyes, she's protesting about the wrong things.
MR. MORGAN: And Kat. I want to thank you for your point of view.
She smiles to herself, her social indignation justified.
I know how difficult it must be for you to overcome all those years of upper middle class suburban oppression. It must be tough.
She deflates and becomes bitter again.
MR. MORGAN (continuing) But the next time you storm around the PTA crusading for better lunch meat, or whatever it is you white girls complain about, ask them why they can’t buy a book written by a black man!