how much time have you spent in a situation where you are a linguistic minority? I have not spent much - but probably significantly more than most Americans, given that I now live in a nation (Japan) where I do not speak the local tongue. Please allow me to assure you, the language barrier is huge when it comes to things such as a sense of community, and the ability to interact.
no one here is saying that Mexican Immigrants are somehow morally inferior because they don't learn english. we are saying that the system is inferior because it doesn't teach them.