Well, it was mostly in jest, yes, but I think it's more than just that, I think it's also that here on the west coast we tend to drive a lot better than people in New York ;)
I live in Manhattan, grew up in the Midwest, went to college in the South, and have accumulated a couple thousand miles of driving in southern California.
While New York drivers are definitely aggressive, accelerating and braking quickly and making sharp, relatively high-G turns, they are also generally polite, focused, good drivers. They let people in when they need to be let in, they take turns when they need to take turns, they don't run lights, they don't tailgate at high speed, they (usually) use their signals, and they are defensive about pedestrians. They have to be this way to survive the traffic conditions in Manhattan and its freeways: if you don't stay on your game, you get into an accident really quickly. If you get over the aggressive aspect, I think they're some of the better drivers I've encountered.
Southern California, by contrast, always drives me insane. Drivers there just don't seem to think about the implications of what they're doing: they tailgate at 80 MPH, they won't let you in if they don't have to, they definitely won't yield to pedestrians if there's not a stark reason to. I've even seen a collection of cars on I-105 honk maniacally while weaving all over and nearly smashing a poor car that had a blow-out rather than make room for him to get off the road and other drivers to navigate around, even though there was plenty of time to see what was going on, slow down, and work around him. The nearest equivalent I've seen in New York, where a car was stalled out on the FDR (a comically narrow three-lane highway down the east side of Manhattan), had cars slowing down and letting traffic cleanly merge around the disabled automobile.
I don't know why there's such a stark difference. I suspect it has to do with a mixture of west coast drivers driving more, and therefore feeling more comfortable in their cars, combined with wider roads, higher speed limits, and fewer pedestrians. But I think both that New York drivers get a bad rap, and at least southern Californian drivers get an overly good score, when people discuss west- v. east-coast drivers.
I can't argue with that. Southern California has some horrible drivers.
Also, we have highways. Lots and lots of highways. Big ones, 6 lanes each way in some places. But SoCal has major deadlock problems during rush hour. The rest of the time they're just total dicks to everyone else.
Something I've noticed in Canada - is each province despises the drivers of the province to their east. So BC complains about Alberta, Alberta about Saskatchewan, Saskatchewan about Manitoba... and so on. Seems the same thing happens west to east down there too.
This is a horrifying thought. The west coast drivers in Colorado are absolutely horrid, I guess it's a good thing we don't have many New Yorkers then ;).