Then there are those who think that just because water is in short supply in California, the same is true elsewhere.
Los Angeles gets around 15 inches of precipitation per year. Memphis gets around 55.
Then of course, Memphis is on the Mississippi River. A "million gallons a day" sounds like a lot to people who are bad at math and are impressed by a lot of zeros.
I couldn't find numbers for Memphis, specifically, but at Vicksburg, MS (not that far away) the Mississippi flow rate is around 5.7 million gallons per second.
Even if the water were actually getting used up (which you correctly point out isn't the case), 1 million gallons per day would only be around 0.000002 of the Mississippi's water.
It's a trivial amount. In fact it's much less than what could even be described as a trivial amount.
The whole "aquifer" argument is nonsense. No one is going to pay to use drinking water for cooling purposes when the Mississippi is right there.
The real issue here is that Musk has become the Emmanuel Goldstein du jour to a certain segment of the population, and thus must be constantly the focus of the Two Minutes Hate.
Do they use evaporative cooling to make the water cool and reuse, and that's where they lose such amounts? If so, it would generate substantial clouds, like some power stations do.