First of all, if the work is properly attributed then by definition it can not possibly be plagiarism. So even if I make a dead-on photographic copy of the Mona Lisa it is not plagiarism if I acknowledge that the work is by Di Vinci.
AI art could be plagiarism if a person fails to give credit to ChapGPT and claims he painted the image himself. Even if the image is 100% not like any other on Earth.
This is not theft by any legal definition of the term. For example what if you go to art school and study art history and then look at the work of many artists over the centuries? Are you not being trained using the work of others? You can argue that those works you looked at were "in public" the same applies to ChatGPT.
Again with no examples, you are just "making stuff up". Or to use Ng's example "worrying about overpopulation on Mars". In other words a problem that might not ever exist. It would be so easy to make your point if you had an actual example of plagiarism.
All that said, it is possible to force ChapGPT to make artwork that is VERY MUCH like a copywritten work. It will do it if asked. But how is this different from simply using a camera to make a copy? Also, either way, asking GPTchat to make the copy or using your camera is not plagiarism if you properly acknowledge the source.
But all search engines will aid in plagiarism if you askit something like "Find an image of Micky Mouse as drawn by Walt Disney". The artest did not authorize this search. He has been dead for decades. The images would be unquestioned plagiarism if you claimed to have created them. AI art is not different from a simple Google search.