I assume you think you’re joking. An angry gesture, probably made because he had nearly caused her to have an accident by cutting in front of her, does not justify murder.
Plus it sounds as if this guy’s driving must have earned him more than one “rude gesture.”
Nobody said it did. My advice is keep to yourself on the road. Avoid disputes. You don't know who's in the other vehicle, what they're capable of or what they just did prior to your encounter with them. I say this from lots of experience.