There are definitely many important things about languages, but I think attempts to preserve traditional language communities have significant risks and downsides as well, if we're talking about maintaining communities of people speaking them living in the present day, as opposed to scholarly study/preservation (the latter of course has little downside besides time/effort). I'm one generation removed from a dying/nearly-dead language myself, and am vaguely regretful not to be speaking it, but also feel a bit lucky to have "escaped" from it into a larger, less-dying language community, and in particular to have (mostly) escaped the cultural aspects of being an aggrieved minority fighting to preserve some ancient spark of glory.

My grandfather's first language was Pontic, a sibling of modern Greek (both descended from ancient Greek, but not mutually intelligible), and it could be fairly called the language of his community even once almost all of them were, erm, "displaced" to Greece (http://en.wikipedia.org/wiki/Greek_genocide). But he was actually pretty against transmitting it to future generations, because of the strong cultural conservatism that he found among a large proportion of those trying to keep it alive. As you say, it's not just a language, but everything it's tied up in isn't good, either: it was often tied up in things like a strong purist/anti-outsiders/anti-ethnic-mixing mindset, a general anti-West, anti-modern-world outlook, and irredentist nationalism (recapture the old homeland from the colonialist Turks, etc.). He'd just as rather his kids grew up as modern Greeks and lose some of that baggage, in part because he was politically left-ish, and in part because spending your whole life looking for ways to preserve/avenge the 1910s, instead of moving on to a focus on being a Greek citizen in the late 20th century, seemed unproductive. That definitely loses something, I'll admit, but I'm not sure the alternative is better; to some extent you run the risk of having people live their lives as some kind of frozen-in-time living museum, a box I'm glad not to be living in.