It seems to me in most Japanese fantasy (including isekai) these days, demons are merely given the role of an agent in social commentary, where humans are the really evil party and demons are much better, even if in the initial setting they were made to look worse, often through the propaganda going on in the human realm. The setting in this series is much more interesting when demons truly are hopelessly evil from the human point of view, even if they can be communicated with. If you consider the picture this episode paints, the demons might be considered something similar to a destructive AI in some scifi, like Terminator. There's no problem with communicating with it, but it's still fundamentally unreasonable and unfathomable.

Unfortunately humans have a tendency to judge everything based on their own standards, which is why the demons are being given a chance in this episode, and the demons are readily exploiting the chance.