Did you read the article? He didn't blame Google. He blamed himself [1][2] and alerted others to a mistake he made that they might make too.

[1] "So what I realized is that I had made a fatal mistake by forwarding my email" [2] "But, I’m not trying to blame Google for this"

Edit: Also, the title doesn't blame Gmail either. "How to use Gmail..." implies that it's something you the user can do not something Gmail does.

or more truthfully: Man fucks up mail configuration in a non-obvious way, does not blame Gmail.