You have to keep cycling and keep your head up. I automatically raise my middle finger at ALL motorists who honk the horn at me. I don't even bother to look if it is a little old lady of Mr. Muscles.
I do the same thing. Flip the bird and keep going; I don't even look at them. Assholes.
I will say, though, that I get honked at less now that I live & work where I can avoid busy roads. I used to ride 7 miles straight down a main road every morning, and back in the afternoon, and I encountered a lot more hostility than I do now, where my route is a combination of a road with a bike lane, an off-road trail, and a quiet residential neighborhood, with only one small section on a busy road.
The dumbest things I have had happen:
- while I was in a bike lane, a lady yelled at me "get on the sidewalk!"
- someone pulled up next to me at a stoplight, I was in no way blocking them or otherwise in their way, and they honked at me while waiting for the light to turn. NO idea what prompted that, other than my presence where I clearly wasn't wanted.
- just a few weeks ago, a guy on a moped actually came up close behind me and grabbed at my ass. It took me a minute to figure out what happened; for a second I thought I got grazed by a car, but then I looked behind and saw the moped. He pulled out in front of me quickly, u-turned, crossing the median in the process, almost got hit by another moped, and took off behind a park across the street. That was the worst; I'm very fortunate that I don't startle easily, because that could have had disastrous consequences, for both of us. However, based on what I saw of his driving and the high rate of moped accidents in my town, I'm fairly confident that he will get what he deserves.
After the moped incident, a coworker actually had the nerve to tell me that I obviously needed to stop biking to work. I replied that actually, I should continue to get to work however I damn well please, and that assholes need to, y'know, stop assaulting strangers.
Honestly, I've gotten to a point where the more jerkoffish behavior I see, the more I want to bike. It gives me a sense of satisfaction to refuse to be intimidated.
Keep biking. It gets easier. In the meantime, start flipping off rude drivers; I think that helps cultivate the proper attitude. ;)
Good luck!