"No? Alright, then maybe you can answer a question for me..."

Guard is practically growling at this line of conversation himself. Who is this mass murderer to give him a lecture about guilt? Or humanity, for that matter?

Just the same, this sure does seem to be one of his buttons - now to see what happens when it's pressed a few more times.

"How is it, exactly, that certain humans can suppress their sense of guilt so thoroughly that they can wipe out entire city blocks without so much as an explanation? When you were staring at those families through that mask, what problem was weighing on your mind so heavily that you deemed liquefying them was an acceptable solution?"

It's pretty clear that this prisoner does not want to be tricked or bargained with. It's also pretty clear that he already feels awful about what he did, and is just kidding himself otherwise. Some people never bother with giving answers until they start asking themselves the same questions.

"I heard some of the report on my way up. The first victim's body was so charred that we haven't been able to identify her yet. All we know is that she was a little human girl who liked kittens. What happened when you found out that part of the plan? Did you just up and volunteer when you got the chance?"