I think that this hierarchy has value, and what it comes to having a 'truth seeking discussion' I think what has been presented is pretty spot on.
However, humans are social creatures. When someone decides to create competition with you by belittling with name calling or ad-hominems, it can be taken as an attack on your status. To the rational part of my mind, what importance is status? Facts and truth don't care about status!
But humans do care about such things. One commenter at funtensity's link above writes:
I'd agree with this generalization, but I'd add that at times in human interaction there is a muddy mix between demonstrating a logical, cohesive argument and addressing the fact that the other person is out of line.The way you say something may signal that you are trying to diminish their status. If you say it with a sufficiently negative tone, it may even be taken as a signal (a generally reliable signal) that you care more about diminishing their status than about having a truth-seeking discussion.
I think the place this gets out of hand is where 'status' (however classified) is too heavily relied upon to judge the merit of an argument rather than simply to speak to status within the group.