I believe that more often than not, namecalling occurs because the namecaller becomes so frustrated he cannot think of anything else to say.
Instead of logic and reasoned argumentation, he looses an epithet.
I've seen this too. Things said and done in anger. I think most mentally healthy mature adults would turn around when tempers had cooled and apologize for their outburst. I think of this as more under the heading of the "shouting" category that I had mentioned earlier.
But, there is another form of namecalling that isn't from anger. It's from intimidation. It's from bullying. I would hazard a guess that we all saw it in some form back in grade school.
IMO, there were basically 3 groups in the dynamic.
First, the power-over namecalling group who attempted to intimidate and diminish the Second group of people who were their targets while the neutral Third group of people ignored it, were oblivious to it, glad it wasn't directed their way, or hoping that their presence would not be noticed by the First group.
That's the sort of name calling I was thinking of and what I thought Mark was referencing.
Namecalling done not in anger, but by a cold calculating choice with the goal of discrediting, mocking, and/or generally insulting. I have seen this done when the argument is being lost and the namecaller chooses the namecalling way as a method of extricating him/herself from the obviously lost argument.
Most people with namecalling bullying tendencies don't walk this earth by themselves. They usually manage to hook up with a couple of sidekicks who provide the necessary cheerleading and distraction that covers that loss. So, I don't think namecalling is always done from anger.
It's also done as a strategy for manipulation and an attempt to control, IMO and for which an apology is seldom offered.