Not any more absurd as suggesting that "other" people should just magically learn a new language. Could you do so? Would you do so?
Of course that's absurd. If they had come here legally, however, they would be on track to learning the language.
Straw man. No one expects anyone to "magically" learn the language, I hope.
But, were I to move to another country to live, I certainly would learn as much as I could, as soon as I could. At least after being there a year, I would expect I'd be able to hold somewhat a normal conversation in the native language of the country, whether is is the "official" language or not.