There once was an old man who lived alone in a small cottage just outside of a town. The man was constantly tormented by an infestation of rodents that ate his food, gnawed at his meager belongings, and left filth and excrement about.
So the man trapped a viper and let it loose in the house, knowing that snakes prey on rodents.
Soon, all the rats were dead. So was the man.
Lesson: The enemy of your enemy is not always your friend.
Photo credit LC Moss, Scottsdale AZ 2015