Wolves in sheep's clothing.
Jesus talked about these apparent dangerous and scary characters: the wolf dressed as a sheep.
I've always thought of this statement - probably because I was trained this way - as referring to dangerous theologies and/or heresies, etc...
But, I think it's much more simple.
Wolves. Violent. Bloodthirsty. Strategic. Hunt in packs. Big teeth. We write parables about them and tell them to children for all these reasons. Don't cry wolf because when that wolf comes, it'll be bad.
Sheep. Calm. Humble. Fluffy. Nice. Cute. We count them when we're falling asleep because counting wolves, well... that would just cause us anxiety.
So, watch out for violent, bloodthirsty, strategic, hunters who masquerade as calm, humble, fluffy, nice people.
Yeah, watch out for them alright, and try not to be one. We have enough of them already, especially in government and religion.