This spine-chilling video is the result of an all-too-common driver error and a inappropriately old-fashioned response by the motorcycle rider.
To explain: The couple who shot the video (apparently on a cellphone) were on their way out to dinner, when the driver of a silver Mazda ahead of them changed lanes on top of a rider on a big sportsbike, apparently not having seen him (although, in light of what happened later, it’s possible that he did see the rider and simply expected him to get out of the way).
At that point the couple in the car behind began filming proceedings, so you won’t see the original lane change.
The rider reacts by pulling alongside the car and shouting at the driver; judging by the hand gestures you see within the next few seconds, the reply from the driver was probably less than apologetic and forcibly impolite.
At which point the rider takes a swipe at the driver’s door mirror; this used to be quite common in the 1970s and ‘80s, on the grounds that “If you don’t use it, you don’t need it”, but is rare today as most cars’ door mirrors are a lot better mounted than they used to be, and you’re more likely to unbalance your motorcycle than knock the mirror out of adjustment.
Certainly in this case there’s no visible effect on the mirror, but almost immediately the car swerves directly into the motorcycle, hitting it hard enough to force it off the road and into an electricity supply pole – and then swerves back into the road and proceeds on his way.
It’s a huge relief a few seconds later to see the rider on his feet and trying to flag down our impromptu film-makers, asking them to “Follow that car!”