Not true.
It's not worth arguing about either because people will see and project what they want on Tolkien's work regardless of what Tolkien and his son say about his intentions.
This is such a ridiculous argument that I don't even know how to respond to it. Black Panther exists because there was no African representation in American comics. The notion that England, the creator of the largest imperial force that spanned across the entire globe, lacks representation in anything is flatly absurd. Again, it's a horrible comparison so, please, leave it alone already.
I don't know what you're disagreeing with here or what the point you're trying to make is. You and the previous poster seem to be insisting that rules set within a story need to be followed or it will break immersion. The races of elves, dwarves, hobbits, and orcs are entirely made up by Tolkien. Whatever evolutionary traits they would have are entirely up to the creator. Tolkien used no source material to base them on.
Per Tolkien:
The man did not set the rules for the evolutionary traits of the fictional people in his story. His descriptions of these groups were vague unless certain details were absolutely necessary. If seeing a black dwarf breaks the immersion of the story for you, it's because you're projecting your own rules of what these groups can or cannot be on to the story yourself. You readily accept that plants like potatoes, tomatoes, and tobacco exist in Middle-Earth despite being unavailable in Europe until the 1400s, do you not? I don't see anyone making a big deal about those rules being broken in this thread. If you're going to insist the story follow European history and tradition then that should upset you as well. I hope you're able to see what I'm getting at here.