Even if it's a whim, it's still something Kai wanted to do; who is this monk exactly to tell Kai what he can and can't do? It's suspicious that he and the other monks are isolating Kai from his friends.
@chonkury and if they were doing it for self interest, they still would refuse that bribe, since Kai is worth more than that (if he wasn't, he wouldn't offer money to keep him)