Moses, peace be upon him, was brought up in a house of a ruler: Pharoah.
He saw their crimes.
However, when he extended his help to a member of his own faction, he found out the corruption of the ruled.
Thus he exclaimed:

قَالَ رَبِّ بِمَا أَنْعَمْتَ عَلَيَّ فَلَنْ أَكُونَ ظَهِيرًا لِّلْمُجْرِمِينَ
– قرآن –

He said, “My Lord, for the favour You bestowed upon me, I will never be an assistant to the criminals.”
Quran 28:17