We don't allow the guests to control the temperature. At Home Depot, for about $16, there is a plastic lockable box that you can install over a thermostat. Not sure if you have this kind of setup or it it's a unit with controls.
Anyway, I know you are venting here and may use different words when talking to guests, but the word "blast" sounds like the AC is going gangbusters and it's 53 degrees inside.
Maybe you should try putting thoughts in their head (I mention this a LOT). "We find it is very comfortable at 76 degrees" or "Since you are out most of the day, 78 degrees is perfect when you leave in the morning, you will miss the heat of the day and when you return in the evening you could set it back to 76 and it will be comfortable all night!" By letting them know a particular range - and that they can adjust it when gone - they will most likely use a setting similar to your suggestion.