@givemersspls
I agree with your points, but I think the author isn't trying to advance this kind of argument seriously. It's been put in the mouth of an antagonist, after all. And to be perfectly fair, she was turning Yuzuru's "I did what's right" argument against him. My take on that is that even if he's pursuing "right", he has to be consistent: if, as you pointed out, Tasuku was right in the landfill episode, then Yuzuru cannot claim the same thing here. He has to decide. If he was unable to talk back to Chihiro this time, it's because he has thrown "right" to the dogs back then. If he hadn't, he could have insisted on there being a decidable standard of right when Chihiro confronted him in this chapter. I don't think the chapter sounds stupid if we look at things that way.
Of course, if we assume that Yuzuru's accepting her arguments and apologising is proof that her point is what the author is trying to advance, then I agree it's muddled thinking to say the least. But I think it is true that this manga is about the protagonist finding tangible motives for his actions, and confronting this kind of decision is part of it.
As for the repetition of "Execution", I think it's just a touch of absurdism. I read that in my mind with the voices of the piglets screaming for his blood in the courthouse.