If a bike enters traffic lanes without a bike lane, it should behave as a car. In downtown Portland, at least, traffic is slow enough to make it easy to do this on a bike. Guys like that put all bike commuters at risk.
But it is easy for bikers to get ticked off at traffic, since they get cut off all the time by either clueless or inconsiderate drivers. You have to be the brains for about 6 people around you at all times on the bike, and that wears on your ability to remain calm when someone almost kills you because they HAVE to make a right turn before the light changes.