Imo mostly the hate is because. The emperor had the power to keep the empress in line, he had the power to see the prince for who he is, not some pawn of his mother. He hasn't decided to get more involved with his own blood son and emphatise that Etienne is being used as a tool, suffering for the sake of the throne.
Just because he doesn't want the empress to get her way doesn't mean he has to always turn a blind eye to his son.
personal trauma doesn’t excuse the trauma you inflict upon others. emperor was despicable to his own son and deserves the hate.
EXACTLY!!! you said it best
I don't like the emperor either, but why the hate? Yes, he is a coward and a jerk sometimes, but remember he was forced to a marriage and was raped! And had to raise a son product of that raping, so I don't blame him if he hates Étienne, but yeah, at least treat him with respect. Étienne is biggest victim here