In fact, Ji Yao had had the privilege to find out the true history of Prince Rui and his Nocru mother. After hearing those details he had finally understood why this monster was the way he was.
It was partly due to the terrible treatment the prince was subjected to as a child. After watching his mother take her own life in front of him while his father stood there and did nothing it made sense why he had a heart of stone.
Yes, this didn't excuse him from the horrible things he did but it somewhat shed light on how a psychopath was born. A psychopath that had no problem killing his own children all for the sake of power. This man moulded Prince Rui into the shape he is in today.
The emperor trembled involuntarily daring not to make a sound and further infuriate this youth. Ji Yao wanted to do more than just throw things at him but he didn't feel like wasting anymore of his energy on him.
