That's not much of an argument. It's just the basic "Man up!" platitude. It can be used against any complaint despite any merits it may or may not have.
And about your other comment, I have to say you are wrong. Morrison's complaint involves Waid and the work he is doing in this comic. It's not like he ran off a tangent and started talking about something else; he is talking about something that also affects Waid and the comic, something that he has discussed with Waid and that Waid has even managed to refute and that he hopes this comic will refute. If we judge the foreword based on how much it has to do with the comic, then it was a foreword well employed.