The officer drew his weapon because he did not know how dangerous a situation he would be in with the motorcyclist and he was in a tactically weak position by having to pivot around to face the person he was stopping. He never pointed the gun at the motorcyclist and quickly reholstered it after assessing the situation was non-threatening. And as you can see in the full video, the traffic stop was totally warranted, the idiot on the motorcycle was a danger to himself and everyone else on the road:
http://www.youtube.com/watch?v=G7PC9cZEWCQ
There are plenty of bad cops out there caught on video doing horrendous things, but I don't get why anyone would use this as an example of bad police behavior -- the cop in this video was totally reasonable and professional.