According to people who have actually read the book, THERE ARE *WOW* RACIALLY DIVERSE CHARACTERS!
So casting them as their respective race makes sense. These folks are pissed white actors didn't get the roles they saw as "white".
Ha, looks like we read the same article, OP!
From it, here seems to be the points:
Now as you may know, Katniss, the main character in the book and film, was described as having "straight black hair" and "olive skin." It's a post-apocalyptic world, so she could be a mix of things, but some pictured a Native American. Blonde-haired, blue-eyed Jennifer Lawrence won the part and dyed her hair dark.
But when it came to the casting of Rue, Thresh, and Cinna, many audience members did not understand why there were black actors playing those parts. Cinna's skin is not discussed in the book, so truthfully, though Lenny Kravitz was cast, a white, Asian or Latino actor could have played the part.
But. On page 45 of Suzanne Collins's book, Katniss sees Rue for the first time:
"…And most hauntingly, a twelve-year-old girl from District 11. She has dark brown skin and eyes, but other than that's she's very like Prim in size and demeanor…"
Later, she sees Thresh:
"The boy tribute from District 11, Thresh, has the same dark skin as Rue, but the resemblance stops there. He's one of the giants, probably six and half feet tall and built like an ox."
Dark skin. That is what the novelist, the creator of the series, specified. But there were plenty of audience members who were "shocked," or confused, or just plain angry.