Rape is one thing. Abusing your power as an agent of the state over a ward of the state to commit rape is worthy of a life sentence.
I agree that ‘under the cover of authority’ is a serious component of this crime. I don’t agree that a life sentence is called for.
Yes it really is the abuse of power issue that is more important. It tarnishes the overall community’s perception of all officers, the ones that do not do this kind of behavior and don’t deserve this perception.
They are officers of the court, their testimony is always default regarded as truthful, they are armed and have a lot more power than average citizens and especially prisoners. So yes, thirty years is appropriate.