The red flush stays affixed to Lan Wangji's ears as he keeps his glare trained on Nie Huaisang.

Just because he knows does not mean he condones. Just because he understands does not mean he condones. His own behavior was as inappropriate as theirs.

Lan Wangji did not want to let such thoughts return to distract him again. For all his anger at these two, it's also directed at himself. He's bothered by it again. It reminds him of his own lacking self-discipline.

"This behavior is unacceptable. Cease, and do not repeat it!"