Nathan: It sounds like you exercised a great deal of self-control and compassion in this situation. Knowing that you had the ability to cause great damage to the kid on the bike may have been the key to realizing that you didn't *have* to cause great damage to him. That the hurt he was inflicting was nothing compared to the hurt you could have inflicted.
But I am sure that you will think through this and come to your own wisdom about it.
Be nice, until it's time to not be nice.