[It's pretty clear from Ren's tone that he's trying to make Shun backtrack on that, and though Shun is just as attentive to Ren's reasoning here, he doesn't look particularly convinced that his own assessment is wrong. Especially if he's used it and hasn't started slipping back down that slope again.

Adding another mental notch to his list of reasons to dislike Hibari - because being trusted with that kind of knowledge isn't something to turn your back on - Shun closes his eyes in what might seem like a concession until he starts speaking again, tone firm.]

And you think not slipping further after doing that is going to change my mind? Call it what you like, but I'm not going to take back what I call it just because you don't agree. I'm not saying it to be nice.

[Whatever it's born of, it's willpower. Shun's own is born at least in part of hatred and desire for revenge, so he can hardly talk.]