When the raid happens where they capture or kill all the rebels, you go and talk to the princess.
You also see flashbacks as part of the nun and her sisters history.
The bad guy in the flashback tells you that owners have the right to beat or kill their slaves.
This is reinforced by another character; I forget at this point who it was, but I remember it being one of the current authority people... maybe the princess.
Also when you talk to the princess she claims that the scarlet law is needed for the country, implying that she also agrees with the treatment part.