I don't think the majority of bikers are that bad, its just due to the nature of bikes when you see one acting like a moron its usually much more spectacular than any bad driver so it sticks in your mind, I have never seen chavs in a Saxo filtering down the motorway at 100mph.
Most bikers are, I believe good riders. Bikers defiantly have a better good/bad ratio than car drivers. Imo this is because you get good drivers, bad drivers and deliberately bad drivers whereas you only really get good bikers and deliberately bad ones, unintentionally bad bikers are very rare aside from the occasional novice.
Why can't we all just get along?