No one should post a picture made by AI and pretend that it was created by him - it's stupid and unfair. I don't even understand the point of such behaviour, he gains nothing for his personal esteem since he didn't really do anything.
But, it's probably for the money, like many things, money makes you stupid.
And I agree with you when you say that they shouldn't call themselves artists just for writing a prompt.
But I think you're wrong when you say that it's unethical for AI to have fed on the work of artists. In fact it is the principle of every artist to be inspired by the work of others.
Everyone has an artistic background from somewhere else, allowing them to do what they do. You wouldn't have the style you have if you hadn't seen the work of this or that artist before. That doesn't mean that you copy or plagiarise what he does.
The AI makes millions of attempts, it can produce a plagiarized image, as we can do inadvertently (sometimes we have the same original idea as someone else, and then good luck proving that you didn't do it on purpose...).
And I think in that case it's the user's responsibility to make sure it's not before sharing the image. (there are plenty of search engines for this, just Google for similar images)
Searching for an image similar to an artist's style can be very interesting for research, and combining it with other styles can create a new one, but it is clear that simply looking to copy an artist's style and using the resulting images as such is quite unfair to the artist in question.
Unfortunately, works such like digital artists are subject to the laws of the market, and that's why I discussed that we should change the labour system - but as it is, jobs move, sometimes this or that job is not profitable anymore.
Digital jobs are bound to be unstable, because they rely on the technology they use.
Moreover, digital artists have themselves taken a share of the market from traditional artists, who produced creations much more slowly, and with fewer resources.
Thanks for your comment, have a nice day :)