I've thought about this comparison to human artists taking inspiration from each other a bit. The problem becomes the scale. A human artist can't look at 5bn images and use them to be able to instantly mimic the style of another artist, hundreds of times an hour.
Consider facial recognition technology. At an individual level, empowering people to quickly see all of the photos they have taken of their spouse through running facial recognition against their photos is useful and harmless. Allowing governments to run the exact same technology against every photo uploaded to Facebook is a massively harmful expansion of the surveillance state.
I don't think training models against 5bn unlicensed images is in the same scale of harm as running facial recognition against an entire country's worth of people. But this example does show that things that are fine on a small scale can be harmful at a big scale.