@Danny627 I'm sorry this happened to you- these guests don't sound like very nice people.
However, what I suspect is that this has something to do with the cost of using your pool. It seems REALLY high, and that's likely what the guests are upset about, although they are using the pool guy as an excuse.
Personally, I don't think it's fair to charge that amount. If a pool isn't comfortable to use without being heated, then it's not really an amenity if you have to pay extra. At $140/day ($150 if less than a week), that's a lot of extra money. These guests were likely simply annoyed at the high charge.
Have you considered trying to work some of that cost into your nightly rate? Or simply lowering the price? I can't imagine it actually costing that much per day, even with high electricity charges.
I suspect that this will catch up with you with your reviews. You seem like an excellent host, but I think this will come back to haunt you in some way. Good luck.