Kirk's neutral expression doesn't break but he's surprised by how forward Sleeper is about the darker impulses. They're impulses Kirk always has and what he always has to keep in tight control. Even after inventing artificial plasma that could act as a meal substitute, he still went after criminals if he felt they deserved it.

Shortly before arriving in Etraya, Kirk had agreed to follow the Justice League's new approach of not killing. What else was he supposed to do? Hernan is his best friend. However, how well Kirk could follow that new rule has yet to be determined. The beast is always threatening to break through the surface.

Kirk gives a small nod.

"It's primal. The basic Darwinism rule of survival of the fittest," he replies, still keeping his monotone.