According to my father, during World War II folks in our Dutch-American community who had continued to speak Dutch at home for generations (after roughly a century in the US) stopped speaking it because bigots can't be expected to tell the difference between German and Dutch (they are too busy with irrational hatred).
Now almost no one in that community can speak Dutch, even though their grandparents were bilingual. One of the many pointless casualties of the fear and hatred of The Other.