I thought, "*You* were the one who scared your son!" If you'd modeled a calm behavior after the near-miss, he would have recovered from any fright pretty soon. Instead, you created this huge altercation that has completely undone him. He's frightened because of the nastiness -you- initiated."
Oh my stars, this reminds me of my dad. I sometimes think he invented road rage. He used to go ballistic if another driver cut him off - he'd race the guy, tailgate him, scream at him, threaten to punch his lights out, you name it. When I was little, this terrified me. He pulled the same stunt when I was an adult, and I gave him what-for, saying "Never
pull that routine with me in the car again. You did it all the time when I was a kid, and I'm sick of it." He kept protesting and trying to justify his actions, saying "But that other guy did (blah)!" "I. Don't. Care."