Do you know this story?
A scorpion needs to cross the river. He asks a friendly-looking frog to carry him across.
“Do you think I’m stupid?” asks the frog. “You’re a scorpion. You’ll sting and kill me.”
“No I won’t,” says the scorpion. “That would be completely against my self interest. If I sting you, I’ll fall in the river and drown.”