I've taken to doing as much of my weekend shopping as poss on my ratty-bike. It seems that with urban cycling comes an amount of getting hooted and shouted at.
I think the trigger is that bikes are a bit inconvenient to drive around. More than this - there is a marketing driven rage in many drivers; With their car they were promised sexual potency, unfettered speed and universal admiration - but it turns out to have been all a bit of a fib. Worse still is the fact that the tosser riding the bike is clearly enjoying it.
I have stumbled across a wondrous response to this abuse. Pretend that you have mistaken them for a friend who was trying to get your attention, give a big smile - and an exuberant wave of recognition. It fills them with impotent-choke-on-their-own-bile-venom-spitting-fury. So should it be.