One time I got into trouble on the job for speaking English.
"Dumb son-of-a-bitch", "smegma-lipped moron", and "baptized on the ignorant altar" are all time-honored English phrases which got me into trouble when I addressed them to and about my boss.
It was that it was in English that caused the problem, too. Had I said the same thing in Portuguese, or Russian, or Mandarin, or almost anything else I could have gotten away with it.
Arf