Graves' book, "HOMER'S DAUGHTER", takes great liberties with one part of the Odyssey, adding characters and worse, if you're a stickler, but I did enjoy that book too.
The thing is...these are novels/pure fiction, though based on much earlier fictionalized historical things and therefore needs to be taken for just that!
OTOH...having blacks or other non-whites portray actual historical people, even though it's all fiction, is OUTRAGEOUS and patently ridiculous! To claim otherwise, just makes a mockery of the whole thing and does a great disservice to the viewer!
Four words -- "Taming of the Shrew". I've seen two stage productions of it, about 25 years apart, and the first one was faithful to the original script (and boy did my school chums have a variety of different reactions), and the second one appeared to be, but they added a wordless final scene where the couple was in bed and the Tamer was giving the Shrew her cut of the money. It brought the house down.
Staging and casting can enrich the experience, so, we'll just have to agree to disagree.
That said, this particular casting (of Troy) is just a matter of policy, handed down from practitioners of "The Agenda-Driven Life", and I won't be seeing it for that reason alone.