Where is it written, or codified, that it is legal to 'act out' against someone who peeved you off? Do you have the right to assault, or cause injury to someone, just because they refused to let you pass them? or because they said/did something that offended/angered you? If someone peeved you off with their driving habits, by going the speed limit, and perhaps decreasing their speed when you tail gate them, if they pulled off to a gas station, and you followed them, and attacked them when they left their vehicle, and they shot and killed you in self-defense, does that make your death THEIR fault, because YOU tailgated, followed, and attacked them? Or would that be you're own fault for not understand that you do not have the right to attack someone, or hurt them, just because they used their right to free speech, and free expression in a way that upset you?
It's probably the latter, because I don't have the right to use deadly force in defense of myself, if someone threatens harm to myself, or my property, because I insulted their religion, or because I refused to speed up [break the law], or get over into another lane, because they kept tail-gating [illegal], flipping the bird, and driving recklessly.
I may drive like a D-bag, but I make damned sure I do so within the limits of Kentucky law. Which, you may or may not know, is surprisingly lax in most areas of the state, and in regards to what LEOs choose to enforce, and not enforce.