I want to make sure I understand you before responding.
You write: "the mechanism of dehumanization that is often at play allowing a perpetrator of violence to see their victims in a sweeping category-level as less than human and more objectlike, directly work to *shield* them from trauma"
I'm reading that as 'a perpetrator of violence dehumanizes their victims to shield themselves from [the pain/shame of their own actions, which would traumatize them if they acknowledged it]'.