I don't specifically believe that people always use language as a barrier. Comprehension is something which we must develop, and sometimes it's a painful task. Not everyone can do this, and some people would pay thousands to learn another language which they may still have great difficulty in comprehending or expressing in the end.
Hell, sometimes I would communicate with someone who speaks the very same language as I, and I would have no clue what on earth he's talking about, due to accentuation of words, usage of dialects, excessive usage of grandiloquence, horrible syntax and so forth. So no, not everyone uses language as a barrier.
However, there are cases where people, due to culture, refuse to communicate with someone who speaks with the native tongue of a rival country (such as two countries with some war history). Or due to political reasons within a country, such as Belgium which is known for their language divide.
So I say it really all depends on culture and the individual in question as if and why they use language as a barrier, but I belive not everyone does this deliberately