I would say that especially for books out of copyright, they are
unquestionably legally in the right. There is no legal standing for "I like books and it makes me feel squicky when someone disrespects them". Nothing stops you from buying old books and using them as decoupage[1] fodder, using them to start a campfire, or making paper airplanes out of their paper.
Moreover, while it is emotionally appealing to some people to want to add some sort of "responsibility to society" to people who own the old books, it's a very emotional plea that can't really be manifested in the real world. As already pointed out in other places, "an old book" itself doesn't really mean much in terms of what its value is in any particular dimension. Plus, I am always deeply suspicious of anything that expands to "Other people, who are not me, should expend vast quantities of resources so that in the next five or ten times I think about this issue for the rest of my life I feel slightly better about this issue" which is what this really amounts to. I think that as superficially appealing as that may be, it's really a very hostile and demanding position to take.
Personally, to the extent that I would want to lay a "social responsibility" on the AI companies, I'd like to see something like they are either obligated, or ideally, just do it of their own free will, to make the scans of the books that are out of copyright available for some reasonable fee (ideally, "free because we like the PR", but given the scope demanding it be free is not reasonable), and without them trying to lay any further claims on the public-domain results. Trading "one old book somewhere, inaccessible to the world" for "a scan of the book and an OCR of it" I would judge a net win for society for rather a lot of these old books, which are by no means "worthless" sitting in some old collection somewhere but would be a lot more useful for being available.
[1]: https://en.wikipedia.org/wiki/Decoupage , since I imagine a number of people won't know what that is.