Okay children, it's story time. Pull up a bean bag chair and indulge Uncle Bart for a minute. I've heard this story in a couple of different places (The Crying Game and a Star Trek Voyager episode, of all places), but sometimes I find that it fits certain social situations.
Once upon a time a scorpion wanted to cross a river. The scorpion couldn't swim, so it asked a fox if it could climb upon his back to make it across.
The fox said, "No! You're a scorpion, you'll sting me!"
The scorpion responded, reasonably, "If I sting you, you'll drown, and then I'll drown because I can't swim."
So the fox agreed, and allowed the scorpion to climb on its back. Halfway across the river, the scorpion stung him. As the killing poison began to seep into his veins, the fox cried, "Why did you sting me? Now we'll both drown!"
The scorpion replied, "I can't help it. It's my nature."
I leave the lesson for the discerning reader.