It might encourage a few people to learn the real language spoken in the movie instead of a conlang which nobody ever spoke outside the movie. The time and effort expended by Star Trek fans learning Klingon might be better spent learning Basque, Cornish, Abkhaz, Etruscan, or Sumerian. They'd learn a language with speakers and/or literature, and if the language is still spoken contribute to its continuity.

This seems to be one of those "why don't you just be productive?" arguments, which tends to miss the point of why someone did something to begin with. There's a reason Star Trek fans learn Klingon and not a real language, they're fascinated with Klingons but not a real culture, so the energy to learn, say, Basque, was never there to begin with.

I feel similar with history, if I am just doing it for entertainment I'd much rather learn a constructed history rather than the real one.

But if Klingon had just been Basque, then they would have been learning two cultures at once. Ironically it's cultural hegemony from evil empires that real hurts these minority human languages.

Adding non-existent words to a language is not twisting it, it's developing it, like normal languages evolve over time. I'm assuming for any language that is chosen we would have enough writing to know the grammar and structures, so I feel like adding words is not a big deal. You did basically preserve a large part of the language though, even if it's had words added.

This is not correct. Language is much more than words. At times you have social structure encoded e.g. via honorifics. You have concepts and phrases that derive from previous experiences.

Whether you take Sapir-Whorf hypothesis for granted or you think that its inverse is true, cultures and languages codevelop.

You wouldn't say "keep them at the bay" in a language used by a land-locked people. You won't call tomato "pomodoro" if gold in your area doesn't have impurites that make it red and not yellow.

You have to understand that language on a very basic level is a construct of a culture that used it. You can't separate them.

And then there are practical reasons. You won't get actors to learn Mongolic language to play Dothraki. Conlangs aim to combine "alien" with "familiar" which is a must in a movie, game or a book.

> You wouldn't say "keep them at the bay" in a language used by a land-locked people.

If you mean to reference the expression “keep someone at bay” (no “the”) with the meaning of holding them back, that comes from “bay” as in “the howling bark of hounds” rather than “bay” as in “a partially enclosed body of water attached to a larger area”. Completely separate etymology (from old French «bay» and «baie», respectively, ending up in words that happen to be spelled the same in English.)

So, a fine idiom for a landlocked people, not so good for a people without dogs.

It seems more culture impacts language, you don't have social structures that are created in language and implemented in culture later. I agree it's a construct of culture though, but I don't know that adding words is necessarily bad.

Why would actors learn a language when they can just learn their lines? If you're already borrowing concepts from other languages why not the whole thing. I don't know if conlangs are better, but I don't think it would be unethical to use an existing ancient language for a movie or TV show.