It's the same story as always. Find something "-ist" (racist, sexist, mysogonist, etc) and inflate the truth to get a reaction and more people reading your exaggerated outrage.
There are currently two black men, a black woman, an asian man (even less represented than blacks) and several background characters who aren't white. But let's focus on making it look racist because there's always outrage in that.
I'm not saying it's perfect by any means (there can always be improvements) but as Danai herself pointed out, it's the most diverse show at the top levels of ratings. If you're going to target something for lacking diversity, at least find a show that isn't the most diverse in its casting.