Plane and Simple
The Dustmen believe that everyone is dead, otherwise why would there be so much suffering in the world? Different being are just in different states of awareness of how dead they are. Their belief that everyone is dead however does not mean they are more willing than others to kill. The Dead believe the natural cycle of coming to terms with one’s death should not be rushed by killing. The Dustmen are also noted for their use of undead minions and their belief that the undead are pure for being the closest being to an understanding of their own deaths.