Can't say I'm totally convinced by your answer there. I recall some pretty brutal comments to people whose only crime was thinking they knew more than they did, or failing to grasp that something rather important was missing from their line of argument. I guess that may appear as unwarranted arrogance to you, but I wonder if you're just overestimating how able most of us are to avoid such errors.
On the other hand, maybe four years of working with kids has made me go too soft on adult foolishness...