Ren Xiaosu felt that Luo Lan was getting too obsessed with supernatural beings.
Chen Wudi had said that Benbo'erba had tried to get him to defect to his side, but that attempt was immediately seen through by his "discerning eyes." As the Great Sage, how could he work for a demon? That definitely would not do since demons did not seek the Buddhist scriptures from the Western Paradise!
Luo Lan had even risked his own life to save Dong Funan just so he could have a supernatural being as his bodyguard. Furthermore, he relentlessly courted her, but Dong Funan did not take a liking to him.
In between, Ren Xiaosu even checked with Luo Lan to see if he might have set eyes on the wrong person. What if there were problems with Dong Funan?
Moreover, by allowing Dong Funan to stay here, it was equivalent to having a ticking time bomb next to them if she turned out to be problematic.