Wow, the social stratification that puts "bikers" into an "untouchable" category is really underscored here: the automobile occupants did NOTHING to render assistance and drove away seconds after witnessing the accident. They weren't even curious as to whether the rider was OK or not. Wow. The motorbike accident was an "oops", but the unconscious display of lack of empathy is the far bigger "oops" in this video.
When you listen to the conversation inside the motorhome where the video was taken from, they were more concerned about getting beat up by the bikers and fled the scene scared. From what I can see the bikers were probably just good-natured people having a fun ride when they optimistically overtook the motorhome at a tight corner. They don't look like the "Hell's Angle" type.
That reinforces my point: the gulf of misperception/stereotype is so vast it overcomes common compassion. There was nothing whatsoever to elicit fear but the fact that they were motorcyclists riding together. The comment about "no room to pull over" is just a rationalization to excuse behavior they were uncomfortable with; the road was not so busy it would have presented difficulties had they stopped in the lane; in fact, impeding the fast flow of traffic is desirable at an accident scene, so blocking a lane does more good than harm. One also has to wonder why someone wasn't on a cell phone immediately dialing 911. Not even the motorcyclists appeared to be doing that, although in the first shocked minutes of a mishap the mind does not think clearly so the delay in calling 911 could be excused, except with that many people I would expect one mind present to do the obvious and call 911 instantly. Finally, the cyclist who crashed was clearly careless, not only passing at a blind curve but riding such that he did lose control of the cycle. It's fortunate someone coming the opposite direction wasn't made an additional victim. So, lots of approbrium to pass around to all concerned here. Not a shining moment for our species.
That is never an excuse for failure to render assistance. Many crash scenes require a temporary halt to all traffic. I almost regret not taking down an impatient cyclist who screamed at a bunch of us to quit obstructing the bike trail -- just before he nearly hit two fire department medics and the collision victims they were treating.