AI only borrows from others, it creates nothing.

This isn't an argument, it's pseudophilosophical nonsense.

But the real artists whose work was used by the AI to make the banner had no choice in the matter, let alone any chance of recompense.

In order to make such a statement you must:

1. Know what model was used and;
2. Know that it was trained on unlicensed work.

So, what model did the OP use?

I mean, unless you're just ignorantly suggesting that all diffusion models are trained on unlicensed work. Something that is demonstratively untrue: https://helpx.adobe.com/firefly/get-set-up/learn-the-basics/adobe-firefly-faq.html

Your arguments havent been true since the earliest days of diffusion models. AI training techniques are at the point where anybody with a few thousand images, a graphics card and a free weekend can train a high quality diffusion model.

It's simply ignorance to suggest that any generated image is using other artist's work.