In a lot of culture the color black has negative connotations because of the association with night when humans are vulnerable because we don't see well in the dark while things that might prey on us do. Nothing to do with being against black people.
I'm failing to see how demons being a separated race with supernatural powers can be seen as racist.
The novel never gave me the impression of being filled with racism. I can't judge other people's sensitivity but I think we should try to put less effort into framing everything as offensive.