The Blind Man & the Cub ~ Aesop Fable #37
There was a blind man who was in the habit of identifying any animal that was placed in his hands by touching it. Once they gave him a wolf cub. Even after stroking the animal he was not sure of its identity, so he said, "I'm not sure whether it is the cub of a wolf or a fox or some similar creature. But I do know this is not the kind of animal that should accompany a flock of sheep!"
Moral: In the same way, bad people are revealed by their features.