Van driver was aggressive and behaved like plonker. He was also right to be punished for slamming breaks and leaving the car in the middle of the road to slap the biker across his head.
That said however....
Let's analyse something here.
Beginning of the footage: we see white van traveling at faster pace than cyclist (we can see that cyclist is looking 2 o'clock towards driver's cabin, and in his own words "I was overtaken by the van"):
40 frames later the van is clearly ahead, still indicating intention to change lanes and turn left. At this point, seeing that van is already in front of our cyclist and still turning, who would you say had better maneuverability - Aggro Yob in 2.5 tone piece of metal or 80kg Spandex Vlogging Ninja on his light alloy bicycle?
However, despite all odds, Spandex Ninja decides to speed up and force the Aggro Yob (still indicating btw) to stay in the wrong lane, taking entire lane for turning left for himself (or is it - two lanes already on this picture - parking bay or lane devider?). This slightly backfires as he's clearly not able to keep the pace with turning van. With the previous "maneuverability" question still in mind, what do you reckon would have more severe consequences to traffic behind, do you reckon - if 80kg Spandex Vlogging Ninja slowed down/moved closer to the kerb to let the van in front clear access to lane for turning left, or if Aggro Yob in 2.5 tonne van hit the breaks between both lanes of traffic and let one Spandex Vlogging Ninja undertake? :
As the Aggro Yob decides to continue without two lanes of traffic plowing into the back of his van and slows down to turn, Spandex Vlogging Ninja finally gets closer (although, he's still behind line of van's cabin, possibly in drivers blind spot) and instead of pressing breaks he decides to maintain the pace and showcase incredible spacial and directional awareness by
screaming "STAY LEFT! STAY LEFT effectively giving vocal permission for Aggro Yob to
stay left/keep turning left
After both turn, Spandex Vlogging Ninja decides to keep chasing the van (still behind cabin) until Aggro Yob finally speeds up to avoid squashing Spandex Ninja between blue Focus and his van. As a token of gratitude Spandex Vlogging Ninja bangs with fist into the side panel, at which point Aggro Yob loose patience, slams the breaks and decides to perform few Millwall massif courtship moves on the cyclist...
What I propose, gentlemen, is that both parties displayed spectacular lack of common sense, but while Aggro Yob's decision to eject himself from the van in the middle of the road was indefensible, the Spandex Vloggin Ninja should actually sit down and deeply reflect on stupidity of his behaviour if he wants to continue unlocking Lance Armstrong streetracer achievements for the next 37 years for what he did, shouted and performed there, on his own video was ultimate, bottomless stupidity.