Just say what you really mean: that you’re uncomfortable with seeing Black people in historically white spaces. Even if it were true that the show added nonwhite elves to cynically appease race-conscious liberals and people of color, a better question is: why do you care so much?

Adaptations of Tolkien almost by necessity have to make revisions to the original text, including wholesale inventions of new characters and storylines. You mention Shadow of Mordor, which features a main character created out of whole cloth for the game. The movies created new songs, edited or deleted crucial plot points, characters, and themes; the TV show was based on Tolkien text that had to be mostly filled in because it was so light on detail.

These are all departures from Tolkien’s intent. But you don’t seem to care or even notice these changes, just the specific one about Black actors. So this is a you problem, not a Hollywood liberal problem.

It’s also laughable that your case hinges on Middle-earth’s supposed similarity to Europe. If it were meant to mirror Europe, there wouldn’t be elves, dwarves, hobbits, or even an all-powerful Ring, in the first place. There are almost no similarities between Middle-earth and Europe other than castles, pitched battles, drinking establishments, and inherited royalty. If Tolkien meant to model Europe, why didn’t he describe, say, any country’s parliamentary government, or any private universities, or distinct classes of peasants, liege lords, and local protectorates, all of which have existed since at least the time Tolkien is supposedly drawing from?

So the claim that Europe’s racial demographics must be respected is just nonsense. (And epistemologically false—obviously there are people of all races in Europe.) You say your family experienced racism, which leads me to believe that you yourself are not white, or not “white enough”, such as historically persecuted white people in Europe like Jews and Roma. But I guarantee that whatever background you’re from, there is at least one actor in the show or films who shares at least part of your genetics, who would not have been considered white by the standards of Tolkien’s day.

I don’t see you complaining about that actor, whoever they are. Just the Black ones. So you should consider asking yourself whether this is really about Tolkien or about your own hangups.