Kudos to OP @OmegaWolf for your restraint. I'd have lost my temper.

My motto is "don't engage the crazies" but sometimes you can't avoid them. I had an incident with a confrontational pedestrian a couple of years ago, who tricked me with a polite "excuse me Sir" - I thought he needed help with something so I stopped. Since then I sometimes carry pepper spray, velcro under the top tube. Never been tempted to use it, but I've practiced with it and it's nice to know it can probably gain enough time to get away when someone seems intent on assault like that.