At the end of the day, language death is, ironically, a symptom of people coming together. Globalization means hitherto isolated peoples migrating and sharing space. For them to do so and still maintain distinct languages across generations happens only amidst unusually tenacious self-isolation—such as that of the Amish—or brutal segregation. (Jews did not speak Yiddish in order to revel in their diversity but because they lived in an apartheid society.) Crucially, it is black Americans, the Americans whose English is most distinct from that of the mainstream, who are the ones most likely to live separately from whites geographically and spiritually.
The alternative, it would seem, is indigenous groups left to live in isolation—complete with the maltreatment of women and lack of access to modern medicine and technology typical of such societies. Few could countenance this as morally justified, and attempts to find some happy medium in such cases are frustrated by the simple fact that such peoples, upon exposure to the West, tend to seek membership in it.
As we assess our linguistic future as a species, a basic question remains. Would it be inherently evil if there were not 6,000 spoken languages but one?