Nipped in the bud

A guy who had spent his whole life in the desert came to visit his friend.

He'd never seen a train or the tracks they run on. While investigating the area around his friend's house he came across some railway tracks and started walking along them. He heard a whistle "Whoo! Whoo!" but had no idea what it was. Predictably, he was hit. Luckily it was only a glancing blow, but he was knocked to the side of the tracks, with some minor internal injuries, a few broken bones, and some bruises.

After weeks in the hospital recovering, he went back to his friend's house who threw a "Welcome Home" party for him. While in the kitchen, he suddenly heard the kettle whistling. He grabbed a baseball bat from the nearby closet and proceeded to batter and bash the kettle into an unrecognizable lump of metal.

His friend, hearing the noise, rushed into the kitchen, saw what had happened and asked the desert man, "Why'd you ruin my kettle?"

"Man," replied the desert man "you gotta kill these things when they're young."