I agree with Mississipi, I had the same thing taught to me when I did an advanced rider course. Natural reaction, when things go pear shaped to want to stop the bike and suddenly grab for the brakes, it sometimes isn't the best thing to do though, getting a tank slapper is a prime example. I was also taught, on a motorway, never get stuck in the centre lane with vehicles on both sides, "unless its slow moving traffic of course", the rationale was to leave yourself an escape route. So the thinking behind, "what will I do if things start to go tits up" is sound, and as said, it changes how you think about everyday riding. I tend to use the rear brake mainly for slow manoeuvring, the rest of the time its a mix or front and rear with emphasis on the front, I would say 80% front and 20% rear. The exception would be when off roading but that's a different ball of wax all together. Looking at this video the rider behind could have avoided the accident had he have been watching what was going on ahead of him, it also looks like he's slammed the rear brake on causing a rear end slide, this is a typical newbie mistake, so it sort of makes sense that this guy isn't a seasoned biker. It was also a bad place and time to make a road safety video, fog, damp road, fast road, and why the copper stood out in the road in front of him doesn't make sense?? He puts himself and other road users at risk.