People often point out that WWX sort of implicitly asked to follow LWJ.
Wei Wuxian spoke, “Thank you for being so enthusiastic. However, your thoughts are quite off. Even if I am attracted to men, I don’t like just any type of man, much less follow anyone who waves at me. For example, I’m not interested in ones like you.”
[…] As expected, Jiang Cheng’s face darkened, “Oh, really? Then, may I ask which type you’re interested in?’
Wei Wuxian replied, “Which type? Well, I am very much attracted to people like Hanguang-Jun.’
[… ] However, as Lan Wangji heard this, he turned around.
His face was emotionless, “Mark your words.”
[… ]Lan Wangji turned back, speaking in a mannerly yet resolute way, “I will take this person back to the Lan Sect.”
However, this not really a blanket permission, and consent is something that is constantly renegotiated: WWX trying to escape is a very clear sign that he is not on board with this plan, regardless of his (insincere) words at Dafan Mountain. But we have to consider the context of LWJ’s actions to understand them, even if we might still find ourselves thinking ‘well, that’s still not a great thing to do’.
Part of the reason is that the last memory LWJ has of WWX is him refusing both his feelings and his help, and then later dying after being hunted by the sects. LWJ at this point in the narrative is unconvinced that WWX would accept his help if he were to explain to him that he knows that he is really WWX. He is also aware of the risks that would come to WWX if he were found by JC considering his history with modao users, and much more if other cultivators became convinced or found proof that he was really WWX. LWJ is, simply put, scared to lose WWX again and his actions are motivated by this fear.
As readers we also know that the main reason why WWX wants to escape is that he believes that LWJ disapproves of him which he believes would become a problem if LWJ were to discover his true identity. This makes it easier perhaps for us to accept the situation–it’s not like WWX is against LWJ or is genuinely scared of him (although he is wary of his intentions at his point). At this point in the novel, we are perhaps confused or suspicious of LWJ’s intentions, but we have not been given much to believe that our protagonist is in grave danger if he cannot find a way to escape.
It is unclear to me what would have happened if the issue with the arm had not sent them on a quest together, but I think it is meaningful that LWJ reveals to WWX that he has known of his identity only after WWX comes back to him, on his own volition, after they have been separated. At least he is certain, then, that WWX is not angry or disgusted by the feelings he confessed, or at least not enough not to choose to continue on this quest with him. He no longer needs false pretenses or to try to protect WWX against his will. Even if WWX did not accept his feelings, he was accepting his help and his company, and that was enough for him.