I told you, we are wired to be more mistrustful of foreign-sounding words than of marked visual differences. I think it says a lot. Then again, knowing us, I think we'd find a reason to be mistrustful of one another even if we spoke the same language.

So much would be lost if we all spoke the same language. And I agree with @holoz0r , all languages are, alas, tongues of war. The only thing that would change if we all suddenly spoke the same language would be we'd be capable of understanding one another's slurs.