A common language unites a people.
Just like France has made Parisian French the langue de riguer and wiped out Breton etc.? While I do agree that everyone should know English, I'm against mandatory enforcing of it. People learn English because they know they need to, to survive. If Spanish becomes the lingua franca int he future, then so be it. Learn the language, what's the harm? Or are people just too scared to learn something new?