Now it seems that the only thing we tend to respect is the unknown, the exotic, because so little of it is left ("biodiversity" etc.)

This bothers me, and enough that I have taken a bit of time
to try and figure out why. Your biodiversity comment makes
me think of the environmentalists' fight to save various
life forms from extinction due to man's encroachment. They are trying to ensure that all life-forms are respected.

And yet, the comment is preceded by the idea of, and is in a thread about, using a common language. So--I shall address that issue. Please note my disclaimer: by the time and location in which I am living, I have no first-hand experience of one language being subsumed by another.
I know that this is currently in progress in Ireland,
Scotland (thanks to Jo's article), and Aotearoa, and many
other places. There are probably almost no native Americans in the contiguous 48 states that do not speak
English.

Interestingly, we are having more and more awareness of other languages, particularly Spanish, and particularly in public signs, etc. I believe this is true throughout the nation, and that our West Coast has more Asian influence than we do, although I can drive a few blocks and see (not read!) signs in Vietnamese.

But what bothers me is that I don't believe that an
overtaking by language is always a sign of disrespect. In some cases, yes, but I think most of the time it has been a
matter of sheer numbers. More of a side effect, if you will, of a physical invasion, than a deliberate attempt to
eredicate a language.

I am delighted to hear of efforts by the Scots, the Maoris,
aborigines, etc. to maintain their language and culture,
and especially to hear that Gaelic may be turning back from
extinction, as Bill Bryson fears in "The Mother Tongue".

The fact that I can see signs written in another language, and have heard of the efforts by the above-mentioned minorities would seem to indicate that the majority DOES
in fact respect them, not the opposite.