Webmasters are not Google's users, searchers (the general public) are. He's not calling Google's users incompetent, he's saying that there is a serious lack of knowledge within the sys-admin and webmaster communities with regards to server setup issues and HTML etc. in published pages.
It's important not to make assumptions based merely on a point of view of mistrust or bad feelings toward Google as an entity. To address Mr. Norvig's comments, in your opinion is there a lot of "technical incompetence" out there? Aren't many indexing problems (such as canonical issues, to take just one example) not related to misconfigured servers? Are badly-indexed pages a result of poor markup? How many sites are correctly and accurately using metadata?