The Dullard alias came from the early to mid 1990s when I started doing things online: BBS and MUDs. People there were using highly bragging names for everything. Finally, I saw one person with the alias that was something along the lines of "The Great One". I decided that I was to do the opposite--I'd let my work speak for itself rather than my alias.
Eventually, I learned that when people complain about my name in a debate, it is their way of admitting that they were wrong. Not only are they out of logical points to discuss, but they are also out of ways to attack the messenger (me). So their only last retort is to make fun of the messenger's name. It is a good end to the debate when I see that. I take it as them conceding the loss without actually admitting to the loss.