I’m more of the mind to say that Will doesn’t feel guilty about his more vicious nature, rather he just resists feeling okay or happy about it. If he’s not happy about killing Hobbs, then he can still say he did what he could in the situation, which is true, but he enjoyed feeling powerful over this disgusting person. After sending Matthew to kill Hannibal, he tells Hannibal he had no other choice. Yes, but how often can a person say they chose murder because they had no other choice and be able to justify it? Well, how does he justify it to himself? So he tries not to think about it, tries to stay neutral, and runs away from it by ignoring it. And as with any cognitive dissonance, it doesn’t, freaking, work. When he kills Randall Tier, then, it’s chefs kiss. Cold acceptance, cold indulgence, and then he can still turn around and say he was just undercover and doing what he could do in the situation.