Oh man, another excellent callback:
It's more fraught because it's after a battle and while he's watching Wei WuXian torture people to death with corpses, but this is the SAME look and attitude he gave his great uncle.
He gets the argument, that the Wens have to pay and "who could be more evil than the Wens?", but he also fundamentally disagrees with the actions being espoused.
His uncle argued to protect what they still had and preserve their culture and heritage, but through inaction that was just cowardice in disguise and would lead to the same ending for them as fighting and losing would, just slower.
Wei WuXian is arguing for the destruction of the Wens in righteous vengance, but through gruesome, clearly mentally unsound violence with a method that is deeply dangerous and risking a further, more permanent slide into violence and madness.
And both times Lan Wangji doesn't argue at all against the spirit of the argument being presented to him, even agrees whole-heartedly with it, but sets himself firmly against the method.
And also offers a counter-argument and a perfect solution.
Without cooperating with the other clans to fight they're doomed and nothing will be preserved anyway - so let's do that. Wei WuXian is visibly unwell mentally and emotionally and being influenced by the resentful energy and what happened to him - so stop mutilating people and come to Cloud Recesses for peace and healing.
And in both cases the person rejects his solution and someone else comes in to sway the argument to two vastly different results.
Lan Qiren stood behind Lan Wangji and the Sunshot Campaign started forming with Lan Wangji and Lan Qiren making the first formal efforts to reach out and gather support for an alliance, ultimately saving the cultivation world and the Cloud Recesses.
Jiang Cheng stood behind Wei WuXian and pushed him to scorn and reject Lan Wangji's offer by convincing him the offer was critical and condemning of him instead of sincerely trying to help, ultimately leading to Wei WuXian being isolated and committing more acts that made him both unwell and earned him a horrific reputation that was his downfall.
Lan Wangji was missing some vital information in regard to Wei WuXian, but he wasn't wrong that he needed rest and healing any more than he was wrong about forming the Sunshot Campaign being necessary for survival.
