Why shouldn't English be the "official language"? The Italians, Germans, Polish, Czechs, French, Russians, learned it when they came to the states, they looked at learning English as something to be proud of? That said, we've gotten by over 230 years without having an official language so why start now?
The thing Conservatives don't like is a sudden distaste for assimilation and that happens in times where you get an abundance of immigrants coming into the country.
Bookmarks