The neg, in its pure form, is designed to confuse a woman who has already displayed a superior attitude toward you. In other words, it is used after she "draws first blood". It is never to by used in an opening situation as the dynamics of the interaction have not yet been established.
The neg is supposed to be mysterious, and have at least two possible interpretations ("Is he kidding? Is he serious?"). In essence, it is designed to convey to the woman, "I'm not all that impressed by you, and certainly not intimidated by you".
The neg is always something that is earned by a woman who has esteemed herself higher than you. It's designed to start to get her dancing to your tune, and to differentiate you from all the others who wouldn't in a million years say such a thing to her.
It's shouldn't be an insult, but rather a statement, again, always presented with a slight, unaffected grin, that can be interpreted 2 different ways.
Regarding the "jerk" argument, I think by now it has been established that the "jerk" possesses many qualities that are a turn-off to women and that we ourselves would never want to become, but who nonetheless do display one of two qualities that come naturally to them and that would benefit us to incorporate. Confidence, indifference, the ability to say "no", things like this are usually found in the jerk, usually amplified to a self-defeating level, but valuable to us if emulated in a calibrated fashion.
The jerk just "IS".., he is unthinking and his personality is unbridled. Even so, I think of the jerk as an ugly apple tree that has a lot of bad apples on it, yet there are a few low-hanging branches with perfectly good, healthy apples that are mine for the picking. I pick the good fruit, polish them off with my shirt, and eat the healthy fruit as I walk away from the tree.
This ugly tree has served me, fed me, and I have no ties to the tree other than that I found a small amount of healthy nourishment which I took and cleaned up before eating.