The first point does seem to be a bit of a thing in the direction of noble savage/naturalistic fallacy, in the way that appeals to stop Amazon deforestation on the basis of hidden uncovered local plants might prove to be miracle drugs that will safe humanity are overselling wonders previously unharmed by the modern world.

That said, the preservation of endangered languages is definitely in of itself a valuable and noble pursuit of knowledge. It preserves our understanding of the past, at the very least. And for something more groundbreaking, there is the whole matter of the Pirahã:

https://news.ycombinator.com/item?id=8772388

https://news.ycombinator.com/item?id=740687