Because conversations can and should (sometimes) meander off on tangents. As interested and engaged people, we should not only always confine ourselves to the topic at hand, but wonder about patterns and parallels and what they can teach us. "Hey, I've noticed that a lot of these critical blog posts often show a lack of self-awareness about ones own failings or contributions to the problem. I wonder if this is a psychological pattern that we should be aware of in ourselves?".
To return to the implicit point that helicalmix appears to be making - timmg was not saying that "a lack of self-awareness makes this post invalid" (in fact, they specifically led with "This is a good article and it does a nice job of explaining some of the problems at Google") - it was acknowledging the quality of the article, and then using the form of the article as a jumping-off point to a related observation.
A conversation which remains laser-focused on one particular topic at the expense of all others is (sometimes!) helpful in narrow technical domains - but expanding to broader context is usually more interesting and more illuminating.
