Being armed, you need to hold yourself to a higher standard than the rest of the sheeple. Flipping them the bird is a way to potentially aggravate the situation, and these are things we need to be aware of. Wasn't there a post here not too long ago where some incident occurred and the other driver went beside them and started waving a gun? It happens, it could happen to any of us. I know if someone started waving a gun at me while driving and I couldn't get away from them for whatever reason, I'd be firing at them.
If you're driving and somebody cuts you off, yell at em at the top of your lungs or cuss at em till you'd make a sailor blush, but past that just let it go and be done with it... no need to honk, flash your lights, tailgate, flip them the bird, or give them any other excuse to continue interacting with you.