That's ridiculous. That would never fly here - almost 1/3 of my wife's classroom are ESL students, and more than a couple of those are recent immigrants with little or no English at all.
Secondly, while I firmly believe that immigrants should take it upon themselves to learn English in order to effectively integrate themselves into American society (umm.. if I moved to Germany I'd want to learn German, only seems natural that if you move to the US you'd want to learn English), I don't think anyone should be forbidden from speaking their native tongue when and where they choose, so long as the things they say meet the same requirements for decency that they would need to meet in that context if they were spoken in English.