But if...

...you don't know what the person is saying then it is justified to think that what is being said isn't worth hearing.
If a person tries to talk to me in, say, Vietnamese (a language that I have absolutely no knowledge of) it doesn't matter to me what was said.
As such, it isn't worth hearing to me, and it indeed wasn't worth saying for the other person.

Say a person who only speaks Hindi goes to a meeting of people who can only speak Ethiopic.
The Hindi speaker had better bring along an interpreter or be a whiz at charades otherwise he'd be wasting his breath.

You see?
The assertion "not English = not worth saying" has an innocuous side too.

Still, I say that mutual understanding is key.
And I don't think that the burden is on those who speak the more common language to learn the less common one to speak with others.

Why should South Americans be able to slide by on Spanish only when other immigrants (like Asians, Middle Easterners, and Hindus) go through the trouble to learn English?
Which is important to keep in mind, especially in the States, because it's not just English speaking whites that have to communicate with Spanish-speaking Mexicans, but every other non-english speaking immigrant as well has to deal with both English-only whites and Spanish-only "LatAms".
Certainly you wouldn't say that they should have to learn two languages instead of just one.

I'm trying to be realistic and not everyone shares our passion for language studies, so it would not be fair to demand that everyone become these walking polyglots so that they can understand each other when the easier way would be to suggest that they all speak the same language.
(And reasonably it would be best to choose the one that most people speak already...or try to bring esperanto into vogue :p

That's basically the way I look at it.