I think almost everything he says is true (based on my own experience with management). The reason this post is good is because it provides very 'quotable' statements. Of course no one will learn how to be a good manager just based on these bulletpoints, but they can serve as a basis of discussion, so for example if you'd like to mentor new managers in your company (and you understand/agree with what the post says) then this can be a good starting point; you pick one quote, e.g. "As a manager, everything is your fault" -- then talk about it at length.