Had something similar happen to me in San Francisco. While I was walking a driver rolled down their window and shouted "white power" at me (I'm white). Very strange experience. At the time I lived in Chicago, walked everywhere, and never experienced that sort of hostility.

Same trip, I ended up renting a car and going to Bodega Bay where I was again screamed at by a driver who was apparently upset with my driving (this was on the access road to the park). The "f" word was used at me as well.

I'm not sure walking explains it all. There seems to be an abundance of miserable people in this country...