The AI arguments I've seen are instead usually justifying it like this: "We're democratizing those skills. You shouldn't have to learn art/writing/coding or pay someone else in order make what you imagine. Therefore, training AI on pirated stuff is worth it for the greater good." So the fact that it will result in artists not getting paid is unavoidable and much harder to ignore in that line of thinking.
To be fair, you can have it both ways. If you buy-and-pirate, and you buy 4 UHDs per year or 10 albums per year, you've put more money into the industry than the average streamer. Admittedly, buying-and-pirating isn't as commonly done for movies and TV as it is for music, but that can be explained by the increased DRM and lock-in.
There is all the difference in the world between the scenarios. The argument's popularity seems to be born in the argument, more popular on HN, that American white / Christian / males (or some subset of those factors) face discrimination by programs to benefit minorities / women.
What is the difference? It is power. Punching up or protecting the politically vulnerable is a completely different act than punching down or empowering the already powerful and oppressing the vulnerable. Punching down causes the vulnerable to be oppressed (jailed or otherwise restricted in who, where, what, when, etc they can do and be), impoverished, and killed - by definition, they are vulnerable. The powerful have their power challenged, which is many times appropriate among free people where 'all are created equal' and have the same rights.
In the case of artistic media - songs, books, etc. - private people downloading art to use it as art are spreading art and empowering themselves at the expense of powerful interest who have seized control of the art. That's much different than powerful people taking the art to increase their own profit and power, and to significantly displace and distort the art.
(I'm oversimplifying for these purposes: The fact that artists don't get paid by the former, and that it's anarchy used for bad things too, are serious problems.)
> socialistic
You're giving away your biases. Only a certain group calls everything they don't like 'socialism'. It's libertarianism or anarchism. Socialists might say, for example, the state should control distribution of media.