You would battle to prove a self defense shooting in this case. Shooting should be your only remaining option to stop the attack when you decide its that time. He should have, and could have driven away! yet, he insisted on confronting this guy. The driver of the X5 could easily say this oke was threatening to kill him so he pulled a knife to defend himself.
Why did he pull over. he was obviously going to try and teach this oak a lesson, therefore putting himself in a potentially dangerous situation.
When you carry a firearm your number one priority is to avoid conflict at all costs!!! You do NOT stop and try and reason with a rage drunk fool! If you shoot a guy, your gun will be confiscated for ballistics testing for 6 - 24 months. Why risk being unarmed because you shot some guy in a stupid road rage case. Rather save lethal force for protecting your family from murderers and rapists!
If the guy in the X5 actually hit his car on purpose he would be in such deep shit, Simply drive to the nearest police station and report it.
If a guy is aggressive enough to intentionally hit my car while trying to push me off the road im not stopping for anyone!
Im heading for the nearest police station.
If he continues to pursue me though, and damages my car to the point where it becomes immobile and I can no longer escape, I now have no other means to defend myself and my firearm will be making an appearance.
And even after all of this, It will first be presented in a safe "low ready" position with a verbal warning that if he continues his actions you will shoot him.