Started my ride home from the metro station as ususal last night. Sometimes I get lucky with the left turn arrows and I can piggy back on that signal, which is what I did (start in the crosswalk from the sidewalk, and blend in to the left turn flowing traffic. A guy in a car who was sitting at the red light, waiting to go straight ahead leans on his horn and flips me off. I was not impeding him in any way. Me being there or not would have had no bearing on how fast he got anywhere. He seemed to simply be upset that I "severely bent" the traffic signals on my bike.
I think I have a better time understanding the driver behind me who gets beligerent because he has to slow down for me and my bike, even though in that situation I'm completely within the bounds of the traffic laws.