The only people taking offense are the people who apparently find it offensive that dark skinned people were cast in this show.
I've said it several times already in this thread. I would have had no issue with the show having cast only white actors. Tolkien's writing left a lot of ambiguity in the descriptions of a lot of peoples and specific characters. I'm fine with the showrunners using that ambiguity to cast a diverse set of actors. That's it, super simple.
Tolkien specifically said that this portion of Middle-earth is not in anyway congruent with white Northern Europe (geographically, archeologically, culturally, or spiritually) and he detested it being referred to as 'Nordic' (as an intrinsically white narrative), so having non-white skin tones where none where specified isn't some butchering of his work. But I will say that it's pretty disturbing seeing the lengths people will go to try to push a virulently exclusionary whites-only agendas. Even if you yourself aren't white, these are still segregationist agendas.
In this thread we've had everything from "black people can't be elves because elves are supposed to be attractive" to "black British actors don't have the right culture to play British people". It's pretty bad.