Language: The Bane of International Harmony?

*Spoken in a deep V for Vendetta voice*
Why is it that there exists a myriad of languages to serve the purpose of communication when there is only one race of human beings? Why do we as human beings strive to complicate matters by having so many languages when one language alone is so complex and misunderstandable to even the most prominent of users of that language?

Why do we throw away the idea of international harmony that can brought upon us if only one language were understood and used by the entire populace of this blue planet for petty things like respect and honor for one's origins? Is not the safety of our people more important above all? The people who say they'd rather die than throw away the language of their ancestors for the language of a foreign country need to open their eyes to see the bigger, glorious picture that is this world, basking in the holy lights of harmony, brought upon us by the use of a single, simple and easily understandable language that every single infinitesimal human on this earth will know. If they do not, Vengeance will be inevitable.....Remember, remember, the 5th of November

*switches back to normal voice*
*cough cough* ahem, sorry, couldn't resist doing that after today. Anyway, what I'm getting at is simply speculating how the world would be if there existed one language that is understood by all. As of now, the only people who are able to talk to every person on this planet and negotiate and reason with them are people have a career in studying languages i.e linguists and interpreters. Peace talks between nations are only possible if both parties know each others languages (which most do not) or each of them hire an interpreter. What would happen if one or both interpreters aren't there? Nothing! Absolutely nothing will happen except for the two parties attempting to communicate and probably end up causing a misunderstanding and prolonging and intensifying the war between the countries they represent. I cannot even begin to imagine how a world with one language would work, but I can only hope that it is a much more peaceful world than the one we live in.