Argument A. No it's copyright violation
OpenAI Sued for Using Everybody's Writing to Train AI - "The class action suit, filed in California, alleges that failing to follow proper procurement guidelines, including seeking the consent of those who produced that content in the first place, amounts to straight-up data theft."

This will affect not only OpenAI, but Google, Microsoft, and Meta, since they all use similar methods to train their models.
 

Argument B. Yes, it's fair use
Thoughts from Creative Commons:
Fair Use: Training Generative AI - Stephen Wolfson
Better Sharing for Generative AI - Catherine Stilher

Thoughts from UC Berkeley Library Copyright Office
UC Berkeley Library to Copyright Office: Protect fair uses in AI training for research and education

Thoughts from EFF: Electronic Frontier Foundation:
AI Art Generators and the Online Image Market - Katharine Trendacosta and Cory Doctorow
How We Think About Copyright and AI Art - Kit Walsh
“Done right, copyright law is supposed to encourage new creativity. Stretching it to outlaw tools like AI image generators—or to effectively put them in the exclusive hands of powerful economic actors who already use that economic muscle to squeeze creators—would have the opposite effect.”

Other countries

• Japan Goes All In: Copyright Doesn't Apply To AI Training

• The Israel Ministry of Justice has issued an opinion: the use of copyrighted materials in the machine learning context is permitted under existing Israeli copyright law.

Legal opinions

It will be difficult to prove, according to IP lawyers like Katherine Gardner
“When you put content on a social media site or any site, you’re generally granting a very broad license to the site to be able to use your content in any way,” Gardner said. “It’s going to be very difficult for the ordinary end user to claim that they are entitled to any sort of payment or compensation for use of their data as part of the training.”

Rebecca Tushnet studies and teaches copyright and trademark law as the Frank Stanton Professor of the First Amendment at Harvard Law School. In this interview in the Harvard Gazette, she talks about some of the broader legal issues around emerging tech. 

It's difficult to remove data from an AI once it's been trained.

According to Google, "Fully erasing the influence of the data requested to be deleted is challenging since, aside from simply deleting it from databases where it’s stored, it also requires erasing the influence of that data on other artifacts such as trained machine learning models."

To address this, Google has announced a Machine Unlearning Challenge, a competition for researchers to foster novel solutions to this problem.

Copyright is only one lens through which to consider generative AI

We Need Smart Intellectual Property Laws for Artificial Intelligence - James Love in Scientific American
Good summary of the issues around training generative AI tools.

Creative Commons defends better sharing and the commons in WIPO conversation on generative AI 

“In particular, since all creativity builds on the past, copyright needs to continue to leave room for people to study, analyze and learn from previous works to create new ones, including by analyzing past works using automated means.

Mr. Chair, copyright is only one lens through which to consider generative AI. Copyright is a rather blunt tool that often leads to black-and-white solutions that fall short of harnessing all the diverse possibilities that generative AI offers for human creativity. Copyright is not a social safety net, an ethical framework, or a community governance mechanism — and yet we know that regulating generative AI needs to account for these important considerations if we want to support our large community of creators who want to contribute to enriching a commons that truly reflects the world’s diversity of creative expressions.”