A man who had lived his whole life in a desert was on his way to visit a friend. He'd never seen a train or the tracks they run on. While standing in the middle of the railroad tracks, he heard a whistle, but didn't know what it was. Predictably, he was hit by a passing train and thrown to the side of the tracks, with some internal injuries, a few broken bones, and some bruises.
After months he had recovered and was at a party at his friend's house. While in the kitchen, he suddenly heard the kettle whistling. He grabbed a baseball bat from nearby and battered the tea kettle into an unrecognizable lump of metal. His friend, hearing the ruckus, rushed into the kitchen, and seeing what had happened asked, "Why'd you ruin my good kettle?"
The man replied, "Man, you gotta kill these things when they're small."