The point is that most of HN identifies themselves - on the Myers-Briggs scale anyway - as introverts. The test labels me an extrovert, yet I do not see these artificial, and frankly invented, differences between all of us.
I also mentioned that this sort of broad labeling is divisive - and I certainly feel this way. I've been labeled as a Myers-Brigg extrovert, and now I have the rest of HN to thank for assuming that I'm a brash, shoot-first-ask-questions-later sort of guy.
I don't see the problem labeling my Dad an extrovert... there's nothing negative about it, and it describes one general aspect of his personality pretty well. Even more so, recognising this aspect of his personality has helped me interact with him in a much more productive manner.