This is kind of exactly the thing though, we all assumed he was murdering cats because their spirits look creepy while following him around, but several other instances in this series have tried to tell us to not judge all of these things by appearances alone. Some of them looked like horror movie monsters but weren't actually the bad guys. Some of them look like sweet, innocent children... until they notice you looking at them. Trusting our eyes, or rather her eyes, isn't always the best option.