Self published, unscientific and hatefull writings like The pamphlet of the Christchurch terrorist should definitely considered as hate speech.
I also stand aloof from this crude and inhuman positions but we should be carefull wehn deciding what is pure racism and what falls under free speech.
So for example, and maybe I am false but at the first glance I can't see tendencys of racism in the book "Ce que penser veut dire: Penser avec Goethe, Heidegger, Rousseau, Schmitt, Péguy, Arendt." It was also published from a classical, long established publisher (Éditions du Rocher) who also published books from Alfred Doeblin or Fritz Lang.
So that is just my humble opinion about that, however I would also remove books from the typicall publishers of the far right (Arktos Media, Antaios Verlag etc.)
Maybe you can implement a filter: if these publishers appear in the metadata, than they should be deleted immedately.