Had pretty much the exact same thing happen to me OP, a few years back on my first bike - albeit without the driver giving me the finger; they just looked straight ahead and pretended I wasn't there!
Doing a 500 mile commute per week now (in a car!), for the last 10 months, I see so much more poor driving than I used to on my 25 mile commute

And the biggest culprits other than woman are men aged (at a guess) 20-35 - it's just all about the ego, they race, block and generally drive dangerously in an attempt to keep this ego buffed!
I see far fewer 'boy racers' these days, it seems the late teens-early twenties opt to drive the same old lowered 'rides' adorned with stickers and hanging cuddly toys... gone are the days of Novas tazzing around (thankfully).
Back on two wheels though, seeing all these 'characters' week in week out helps me to keep my spidy senses on the lookout, having said this, I'll probably be posting in the hotter months telling you all how I got hit off by someone I hadn't pinged.
As for smacking cars in disgust, I like the idea, but I prefer the idea of opening a door instead
