Helmet mounted headlights are awesome... (well the high power ones are at least). Presuming that someone pulled that kind of aggressive stunt on me, and my helmet light was off, I'd fire it up. Presuming that it was on, I'd make sure that he's got so many spots in his eyes that if it came to a punching match, he's going to be doing it blind. Mace would be a good idea as well. After that encounter, I'd certainly be reporting it to the authorities. Posting it here however probably wouldn't be the best move, as (and I know this from 1st hand experience) lawyers do data mining when bikes are involved in an incident.

For the record, at night, I use a MiNewt X2 on the helmet (low or off on MUP's, low on roads), a MiNewt 600 on the bars (walk mode), and I have a MiNewt 200 on the bars (typically off on MUPs, flash on roads), the 2x PB 5LED Beamers are only used as a emergency backup.

I'm thinking strongly about picking up a GoPro (or similar) camera for weirdness like this.