Answer:
The right thing to do is to speak up! As a citizen of the United States of America, you are entitled to your freedom of speech and seeing an inhumane act been carried out that does not go well with you, you simply call out the person and gently explain to he/she that the individual has stated humanitarian and civil rights and has to be treated justly.
On no grounds should that be condoned as it is an assault regardless of the fact that it was an interrogation.