They sound like morons. You need to speak to them in the "moronic language". Remember, guns speak louder than words and even a complete moron will normally recognize a gun.
Walk into their house with a large double barrel shotgun. Point it at the first running fan you see. Tell them they have 20 seconds to shut the energy wasting fan off, or it's gets blown to kingdom come. Allow them 20 seconds to turn it off. If not, pull the trigger (wait till they are out of the way). Go to the next fan and repeat. By this time they will likely shut off the fan, knowing you mean business. Continue to all six fans. I can guarantee you WILL get a response (one way or the other).
Note: If you must shoot the fan, aim for the motor or the power cord. Dont hit a fan blade, the bullet may come back at you. Besides, there will be more "fireworks" when you hit the electrical parts, which will add to the excitement. It's unlikely you'll have to actually shoot more than the first fan once they get the picture and know you're serious.