Why is the adoption of a single lingua franca NOT an attractive alternative?

"...Because it involves the dominance of the chosen language, to the disadvantage of speakers of the other languages, and raises the prospect of the other languages becoming second-class, and ultimately disappearing. Since the loss of a language often involves the disappearance of a distinctive culture, and a way of thinking, this is a loss that should matter to everyone." http://www.essex.ac.uk/linguistics/clmt/MTbook/HTML/node5.html