I'm a little late to the party, here, but isn't throwing a "deadly missile" at a moving car a felony? The punk's actions could have made John swerve and collide with other vehicles resulting in multiple injuries or death. Also, being as it was coffee, *intent* to injure John with a hot substance could have been there. If any coffee got on John, would that be battery? Just some thoughts...
We can't understand the mentality of punks like those because their thought process runs just a touch below that of the critters living at the bottom of the sewage treatment facilities of most large cities. I think you've already decided that pursuing this would not be worth the effort in view of the expected outcome and you are probably correct.
As for the video being on-line, I don't know about the liabilities there. I doubt the guy worries too much about what his mama thinks. He might be more concerned with his employer (if he has one). If someone who knows him sees the video they most likely will mention it to him. Could his friends be razzing him about the video? From the video I would think that he got a good look at you, too. It takes a real lowlife with little respect for others' wellbeing to do what he did...he definitely could have caused you to wreck and injure/kill yourself or others (that may be why it's a felony?) Could the video further anger the punk to other actions? I have no idea of the chances of John running across this scumbag again, I'm not famliar with big city life, but is putting the video online really going to help John sleep well at night?
I believe in defending myself, family, friends, etc., and I believe most LEOs believe that we have the right to that defense. We live in a world of action and reaction. To me, personal defense goes beyond the physical/mechanical aspect, it also deals with your own mentality of how you deal with situations. Among those things is when and where you cross over from defensive actions to offensive actions...sometimes they are the same. Don't let the perps control your actions.
Just some rambling...