I am not too sure about the gun, seems like a good way to make sure someone gets dead, and that probably would not be the gun in the truck but some innocent bystander. (btw, I am a gun owner and pro 2nd amendment, so no anti) The best defense is a good offense. I would suggest if anybody is on a group ride and a jerk in a car/truck follows you to the end, then gets out to start a fight, don't even throw around insults in the beginning. Just knock the **** out of him. Hit him hard and hit him first, don't even give him the chance to get the knife out, claim self defense later.
I don't really know how much I am just joking about that.