I trust my bank a whole lot more than I trust Anthropic
Those who argue copyright infringement have a somewhat compelling claim, but stolen is a little out there. Especially since text I have written has provably never been stolen, making "every piece" impossible.
The underlying trouble with the copyright infringement claim is that it forgets that copyright was extended by the people as a construct to help foster innovation so it expected that the same people would ignore/revoke copyright claims where the product of its use is seen as a greater innovation. Copyright is but a human-created tool, not some natural law of the universe.
I understand also that not everyone sees AI as a worthy innovation, but societies do not function on the whims of a few people.