I agree with you that it is frustrating if a story that used to be accessible publicly is no longer accessible, but I fully support the author's right to control how her stories are distributed. Of course once a story is published on the internet any such control becomes very difficult, but not entirely impossible--as proven in your post.

If, for whatever reason, an author wants to pull her stories from public archives--and this includes the Wayback Machine--she has a right to do so. I do not consider it insulting at all. I consider it the creator's right.