[epistemic status: not sure if endorsed, but I’m just going to throw it out there]
Linguistic rights are pretty uncontroversial. Even the UN endorses it:
Considering that universalist must be based on a conception of linguistic and cultural diversity which prevails over trends towards homogenization and towards exclusionary isolation;
Considering that, in order to ensure peaceful coexistence between language communities, overall principles must be found so as to guarantee the promotion and respect of all languages and their social use in public and in private;
Considering that various factors of an extralinguistic nature (historical, political, territorial, demographic, economic sociocultural and sociolinguistic factors and those related to collective attitudes) give rise to problems which lead to the extinction, marginalization and degeneration of numerous languages, and that linguistic rights must therefore be examined in an overall perspective, so as to apply appropriate solutions in each case;
In the belief that a Universal Declaration of Linguistic Rights is required in order to correct linguistic imbalances with a view to ensuring the respect and full development of all languages and establishing the principles for a just and equitable linguistic peace throughout the world as a key factor in the maintenance of harmonious social relations;
So what are the advantages of linguistic diversity? Well, for one thing, every language that goes extinct is one less language for linguists to study, and that makes it harder to figure out how exactly language works. For another, many languages have literature which has not been translated and, without speakers, may never be translated. Some things like poetry are entirely untranslatable.
This seems to me to be less an argument in favor of reviving dead languages and more an argument in favor of a sudden frantic burst of linguists and translators.
My position here is shaped by me being a skeptic about the Sapir-Whorf hypothesis. The weak form of Sapir-Whorf has been validated: languages that use “north/south” rather than “right/left” have speakers that remember where North and South are more easily; speakers of languages that make more color distinctions have an easier time remembering colors. However, the strong form has not been validated, and I don’t think it will be.
Think about so-called “untranslatable” words from other languages. It turns out that all of those words are, in fact, translatable; it’s just that you need a paragraph to translate them, rather than a sentence. There’s nothing inherent in the English language that means we can’t express a particular concept. Of course, it’s easier to express a concept if you have a particular word, but English has never had any particular difficulties inventing words that its users need. The language which brought us “one-reply bitch”, “lackoass”, and “post-fartum depression” will not be long stymied by concepts without words.
As for the downsides:
The burden of linguistic diversity falls disproportionately on those marginalized. As a native English speaker, I am at an advantage in science, trade, and even tourism, because my language happens to be the lingua franca. A member of a group with a dying or dead language is in one of two situations.
First, they’re raised as a native speaker of a language with a few thousand other speakers, and then they have to learn English. If they’re not linguistically gifted– several of my friends are cognitively incapable of learning a second language, and I imagine this is not a malady limited to native English speakers– they might be confined to jobs that only require the ability to speak their native language.
Second, language preservationists want to make them learn the language. I notice that no one’s language preservation tactics involve making me– a white, upper-middle-class American– learn Quechua. They want to make the people who originally spoke these languages learn them. These efforts disproportionately affect poor people, people of color, and people in developing countries, for the simple reason that those people’s languages are the languages that are dying. Even the white, developed countries that have language-preservation efforts, such as Ireland, are countries that have a long history of colonization, imperialism, and oppression.
The problem is that all the effort being put into preserving a dying language is not being put into anything else. The school hours that Irish students spend learning Irish are hours that American students are spending on science or math. The money spent on state-owned television stations in a dying language is money not being spent elsewhere. Is it really worth directing that effort?
Now, I’m not saying we engage in the deplorable practices of wiping out languages. We should not punish children for speaking their native language, force people to change their names, or require workplaces by law to only use the preferred language. But I am suggesting that we leave it up to individuals whether they want to preserve a language. I suggest an end to deliberate efforts to support a language. There’s a difference between cold-blooded murder of a language and taking it off life support, and we’ve too long equated the former with the latter.