The labor theory of value doesn't work for documents any more than it works for anything else. If I do something that's easy for me, and it's valuable to you, you'll still want it. If I do something that's difficult for me, it will be less valuable to you, because the difficulty I have with it implies that what I produce will be of lower quality.
This is all equally true of automatically-generated documents. If they're valuable, people will want to read them. Whether it was unpleasant for someone to create them isn't a factor.
So where is this slogan coming from? Are people just afraid to admit that the documents they're getting are valueless?