Oh I know, it's pretty much my least favorite thing in the whole of Star Trek. I've ranted about it many times.
I did have a revelation about it a couple years ago however. I was watching TOS and listening to the aggressiveness Kirk used in speech as well as other characters I decided that they made Archer like this to connect him to the Kirk era. After all these humans aren't just like us, they've come out of a long recovery following a horrific third world war.
This is what I originally posted on it in my Archer's Aggression Explained! thread, LOL
"I have been watching all of TOS again and having finished that I just watched Broken Bow and you know.. the human aggressive reactions fit right in with Kirk and McCoy. You don't think Captain Kirk would stand around letting the Vulcans look down on him do you? He'd be volatile. McCoy would be all huffy and pissy about logic and having no heart. This is the first time I've seen what I perceived as embarrassing behavior on Archer's part as part of the Trek continuum, connected to the great Captain Kirk."