Although Xuanming isn't as ancient as the Gua Tianshi, he is an Impermanence existing since ancient times, with a life scale and perspective vastly different from ours. Moreover, he grew up in a cultural background entirely unlike that of modern society, which makes the foundation of his values radically divergent. To empathize with such a character is indeed challenging for both Little Bowl and me.
However, since it's likely we'll directly clash with him in the future, even though we know it's difficult, we can only speculate about his mindset by putting ourselves in his shoes. Why did Xuanming remind Little Bowl, aside from my previous guess of "can't bear to watch"—could there be other reasons?
For Xuanming, who came from an era where human sacrifices were deemed normal, capturing people for sacrificial purposes might have been understood and viewed as a legal process by both the captor and the captive, whereas this is not the case in modern times.