Wrong! The guy overreacted from the minute he picked up on Matt's initial comment, which was not intended to be heard. This was exactly about a driver not liking his driving being criticized. The bike is irrelevant, but the car and the way it was driven, plus the fact that the guy thought he could bully a young lad, was exactly the cause of the incident.The thing that provoked the guy to get in Matt's face was Matts sarcastic "See ya!" as he rode off.
Take the bike and car out of the equation. If an 18 year old started mouthing off at a random stranger in the street the likely outcome would be the same.
In Transactional analysis terms, Matt's (Immature) Child Behaviour drew out a (Critical) Parent Behaviour response.
http://www.businessballs.com/transact.htm