[If nothing else, that staring at the ground is concerning enough to tell Shun he might want to make some sort of concession here. While he tends to impress realism upon people as much as he can, it seems like it might have been a little much here.

So he leans down a bit, his expression softening slightly. It's not much, but it's marginally better than the hard neutral he's largely been trying to maintain.]

If that's what you believe in, then there are ways to still make it work. It's not always necessary to agree with someone who sees the world completely differently than you. [Which seems to be the case with her and him.]