The authors of the Old Testament for some reason failed to appreciate the cognitive benefits to multilingualism. They also didn't realise (as I believe Douglas Adams pointed out) the peace-preserving benefit of not being able to understand what your neighbour is saying about you. Or the possibility of machine translation which some day will remove that benefit again :)

Well, in all seriousness, "saving a language" can mean many things, beyond "using humans as storage devices". On the one end of the scale, it can simply mean "not trying to eradicate a language". There are countless cases throughout history where speakers of central/majority languages have tried eradicating other cultures or languages, see e.g. "The termination phase" in http://galdu.org/govat/doc/mindeengelsk.pdf#19 about Saami.

Or, getting slightly more actively involved, it could mean trying to be supportive of the people who actually want to use their language – like creating software/web site localisations, book translations, spell checkers / other language tech. It doesn't have to mean forcing people to learn a language they don't want to learn, just so they can be studied by linguists :-)

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I was a bit disappointed by the "need to save cultures" paragraph as well; tighter-knit isn't necessarily better, especially not if it means active antagonism against other groups. But you'd think there would be less antagonism between groups if speakers of a non-central language have the feeling that the language they grew up learning, the language their parents spoke to them, the language that's nearest to their self-identity, is considered by the majority/central group to be somehow "worthy" (and not just something that should go away because it's an annoyance).