I'm going to go out on a limb and say Dan knows people bullshit, but it would be very weird to say "well, I guess I can't criticize the bullshit" just because someone else doesn't care about the truth.

To your point about people enjoying the work, they're still allowed to. Anyone can read what Dan wrote, and say "I enjoy this work despite the fact that (almost) none of it is true." I do this with Marvel movies, for instance. I do suspect that many readers did not realize how phenomenally bad Kurzweil's projections are, and would be disappointed by realizing that they are.