To quote the movie Spiderman: With great power comes great responsibility.
You're actually quoting the great Stan Lee, creator of many Marvel heroes.
And this sounds like a guy got mad at traffic and just wanted to get people out of his way in a fashion that yelling and honking his horn was apparently not accomplishing. That being said, no person that does this is a completely sane and rational person; hence reasoning with them is often a moot point.
So reasoning is out the window. So your other options are to fight or get away. Firing a weapon in traffic from a moving car to another moving car is not something that we train for. If people are highly mobile, there are too many variables and too many innocent bystanders at risk. Not to mention that you have motive and opportunity to RETREAT. For God's sake, you are behind the wheel of your car; the device which people most often employ to make a hasty getaway. When in Rome, and all that...
If you feel the impulse and urge to exercise your sense of civic responsibility, then try your best to get his plate number and call the police. Well, call the police anyway, but this way at least you'll have more to tell them. Pulling a gun out in this situation would be a bad idea.
_________________________________________
Officer: Hello, Mr. Disgruntled Driver. Why did you pull your gun and intimidate Mr. JGant?
DD: Well because I saw his gun first and thought he would shoot me.
JG: No freaking way! He pulled out his gun FIRST!
DD: Nuh uh...
Officer: Well you're both going to jail because 3 other cars all have damage from you neanderthals trying to shoot and get away from each other.
Sound like something you really want to be dealing with?
~LT