Spirit. Tainted spirit- it is complicated. Justice is Justice unless Justice is Vengeance- preventing a spirit from fulfilling it's purpose is one of the many ways a spirit becomes a demon. We help Justice fulfill it's purpose- we run less risk of there being an incident.

[ Setting Anders aside might not be enough- if no one comes to him? What good will that do. ]

Wardens are injured often enough but not on the basis they would need to feel fulfilled. And...even with the Inquisition's judgement passed there are those that might act against him. Better that someone can mind him and prevent either an incident or an altercation.