I can generate a picture in stable diffusion in about two seconds with my GPU. Running a GPU for two seconds doesn't take much energy, almost certainly less than 2500kcal. Back of napkin math for a 250W GPU spending about 4 seconds at full blast says it would take about 1000 joules, which dividing by 4184 to get it into kcal, would be roughly ~0.24kcal. It is literally 10000x less energy than the number you provided me.
Even if my math is off by a bit, let's assume that it's off by two orders of magnitude, it would still only use 1% of the energy compared to a human.
So the basic math you gave me supports what I said. Unless you find an error, which I don't think you will because this math is trivial.
This isn't counting the energy cost of training and gathering the data, which sure might be expensive, but if we assume the models already exist then the energy cost of generating a single image is pretty negligible.
Now, a counter point you could make is that since it's so low-effort to generate an image with Stable Diffusion, and since the image might not be very good, you might end up generating thousands of images compared to the one you would have paid a human to do, and yeah those numbers get more complicated, but that wasn't what you claimed, you claimed "if you were to generate one piece of AI art, the energy expended is several magnitudes higher" which is trivial to prove wrong with basic math.
But also, counting calories like this is bad anyway, because it's making an assumption that all energy is equally damaging to the environment, which is not true. If the energy used to generate these images was coming from a centralized electrical plant, particular something using solar or nuclear, that is considerably less bad for the environment than a human eating meat. The world beef industry has millions of cows that are all farting and burping and shitting methane that is destroying our climate.
That's what I was getting at when I said the numbers aren't as cut and dry as people keep asserting.
Feel free to check my math and prove me wrong, I'm a grown up, if you find concrete evidence that I'm wrong I'll read it.
ETA:
Also, did you make an account literally just to respond to me? Goons are following me around now?
Another ETA:
I forgot to point out that even if the electrical plants are coming from fossil fuels, which is still annoyingly prevalent in the US, having the energy production centralized means that we're much more easily able to capture pollutants compared to something like cow fart or a cow burp, which pretty much immediately goes straight into the atmosphere as methane.
Now, an argument you could make is that AI art is shit so any amount of energy expended on it is a waste of energy, and that's a better argument than the stupid and objectively wrong one you made.