In Kentucky it is. All you have to say is, “That video of Reginald Denny kept going through my mind.”
In Kentucky, if you fear for loss of life or great bodily harm, it is legal to use lethal force.
We just had a case where a guy was the aggressor in a road rage case, but he was only verbal. The other guy then came at him with a baseball bat, at which point he shot the guy with the bat dead. He was found not guilty. He feared for his life of great bodily harm (one whack with a bat can kill you), justifying his use of deadly force. Who started it is not germane. It’s who escalated it that matters.
Also disparity of force comes into play. You might be able to use greater force than othersise if you have disparity of force issues on your side.
Surprise attack/ambush, being just one of many examples.