Joke only half-describes how I read it. I used to be a regular reader of the Dilbert blog and the post in question actually fit his MO perfectly. Scott Adams is (or tries to be, or claims to be) writing posts with opinions he knows to be wrong, which may or may not be humorous, with the intention of making people think about why they're wrong. My initial impression upon reading the original post is that this was just another case.

While, on the one hand, I can agree that people can't be blamed for taking it at face value when it's quoted elsewhere, I think it's irresponsible of people to take it at face value in the context of his blog without even stopping to check anything else he says on there. The nature of the things he says becomes quite clear pretty quickly.