just from watching the first 30 seconds or so it's clear the bikers have a god complex thinking that they can take up the entire road doing as they please... now this is not to say car and other road users don't do the same.... but in sheer numbers it's a lot to keep track of.
from the start you can hear bikers repeatedly using their horns... that is a HELL of a lot of potential dangers to try and be aware of/keep track of so even if the biker wasn't trying to brake test his mates all giving the tooters is a good probable cause why the first bump took place as the driver could have been trying to see if there were any other dangers and didn't count on the rider in front casually slowing down for what looks like a chat. also didn't help the lead up to that the bikers are all over the road, either side in very close proximity...even sharing the lane along side the RRS!!!
may be British thinking but aren't you supposed to give bike the same space as another car? yet they are the ones closing in on the car and themselves.
I would be pooping myself in that situation, partly because of intimidation of a hell of a lot of bikers but more importantly because there are a hell of a lot of potential hazards weaving incredibly close to my car! I've before had just 3 chavs on scooters "surround" my car when approaching a roundabout, pretty much one on each front wing and the 3rd on the back wing!!! so poor guy for having to be put in that situation to begin with!!
as for the remaining 5 mins I'll watch later...but ok he hits the guy
combination of bad luck and the motorcyclist being to close to start and his mates creating unnecessary distractions. then the did stop and well... dunno what was said but I again would be bricking it having my car with potentially a family with me and having a lot of "potentially" angry bikers all looking at us, now I say potentially because all you can see is their eyes....
him running over the first bikes.... not the smartest of moves but I would probably try and do something similar to get away...obviously a clean get a way would have been preferable, then just report to the police after and say you were fearing for your life.
after skipping the video though some parts i've seen are not on like intentionally blocking off major roads and approaching the guys car in what looks like a heated manner and then try to open/force their way in. it's because of things like this that give a bad stigma to bikers.
tl : dr - situation may not have happened if the bikers we behaving a bit more orderly, personally think the guy was within his right to run due to fear but could have handled it better and the bikers were completely out of line with all of them giving chase like a vigilante mob especially trying to force entry to the car if the guy had a wife and kid in there or not!!!
*prepares to have opinions slated*
can note that I do have a hand full of biker friends and some look intimidating as hell but some are the nicest and most helpful people you can meet