Language is indeed a differentiator, and in a way a way for nations to control and dominate their population. By allowing other languages to exist, what will quickly happen is a dilution effect, as other more popular languages migrate into a country's territory.
But does all this make sense? Your post has really got me thinking about how this might not even be relevant in a couple of years' time, because as technology develops day by day, it shouldn't be long before "live" translation is a reality.
I liked your approach to this subject.
At the moment, there's an ongoing discussion about emigration in my country. Right-wing political groups believe, even though the figures and statistics don't show it, that mass emigration can lead to an increase in the feeling of insecurity and crime levels. I think that much of this feeling that some people refer to is due to the "unknown", to the fact that there is no language that can serve as a bridge to dispel fears.
This is my question. Does it matter? Languages come and go.
That is part of it I think too. It is also that we don't like unfamiliar, including unfamiliar sounds. It is like living in an old home (I do) but all the noises are known to me now. When I go to someone else's place to sleep or a hotel, then all the "foreign noises" keep me awake - well they did ... know I can sleep through anything :)