Narcissistic personality disorder is a condition in which people have an excessive sense of self-importance, an extreme preoccupation with themselves, and lack of empathy for others.
This falls perfectly under my previous number 4 - grasping at straws while descending into any desperate attempt you think might help you.
This one is a classic and predictable defense mechanism for those on the losing side of any argument.
Let's sum it up: The guy who has completely owned you in the argument simply MUST be crazy somehow. So you do an internet search and label your debate opponent as whatever you decide he must be in your own personal "diagnosis".
That's the ticket, because it'll sure distract from how terrible your argument has been.
Once again, it must feel great for you to know that you're nothing special and do the same things many people do when they realize they've been owned in a debate and can do absolutely nothing about it.