This view is from a modern historian called John Man:
Throughout history, politicians and writers wishing to criticise their own bosses have directed their venom at substitute targets whose character and actions resemble those of the real objects of their remarks. And in addition to his historian’s perspective, Sima Qian had deeply personal reasons for such criticism: he was the victim of a gross miscarriage of justice (his castration) that left him with a powerful motive to criticise his own emperor by exaggerating the truth about the First.
Man J, 2008, The Terracotta Warriors, De Capo Press, Philadelphia p.18