The flaw in this argument is the word "artist". If you remove all the pictures from the data source, the AI isnt capable of generating anything. Because it's not an artist.
Second, your Outsider Art is something completely different, funnily enough a strawman. Surely you're not claiming that the creators of outside art have literally never had any sensory input in their lives? Or do you really think that one painter in two timelines, in one blind and in the other not, would paint exactly the same stuff?
Only a bodyless, artificial brain cant draw anything, blind.
See this link, lots of recent works in there.
https://en.wikipedia.org/wiki/Harry_Potter_influences_and_an...
No reason you can't apply that framework to AI.
Where AI might get into more trouble is that you might be able show literal copying in a way that it's impossible to do in a person mind. Like saving chunks of a work into its model.
Now if you are the company selling this product, how many people are feeling wronged and will sue - that's the class action part?
If you use the product to generate an image that is very similar to someone's art and they feel wronged and sue, would you still use it commercially?