You were not his problem but he clearly used you to vent what ever was. There is so much bicycle & foot trafic in the Cambridge / Boston area that for anyone to get upset over what you were doing is insane. I drove tractor trailer in Cambridge / Boston for years in the scientific medical field. I couldn't even imagine getting upset over bicycle / pedestrian traffic. Make use of your cell phone camera or video feature. That behavior will not fly in the Boston area. I am sure he wouldn't like finding himself on the 6 oclock news with a video of him freaking out.