The answer is in the article, oddly enough.
The BBC is at one level all about free speech, uniquely funded and good for you. At another level it is deeply tied into the military establishment in the UK. Since the beginning job applicants have had to pass the Room 101 test and that is a real thing - any socialist types simply did not get employed. They would not be blacklisted and unable to work in the industry, however, the commercial channels (ITV) did not pay for training, you had to get that from the BBC and then you could work elsewhere thanks to that experience.
To quote Napoleon (the old enemy) "Four hostile newspapers are more to be feared than a thousand bayonets." The BBC has approximately four TV channels that shape the minds of the British public. Consequently people in the UK are highly invested in a set of ideas that cannot be thrown out on a wholesale basis.
From time to time there will be high profile events that get reported by the BBC in a way that is not consistent with facts on the ground. Yet people will attend such an event, go home and, despite seeing events with their own eyes, decide that they must have understood the situation incorrectly to believe what 'Auntie BBC' said, to then take that on as the 'correct' interpretation of events.
To think otherwise, i.e. to 'believe' one's own eyes requires a subversive mindset or, as is more likely to be the case, a conspiracy minded mindset where everything from moon landings to flouride is up for reinterpretation. We have all met those types of people - 'nutters' - so those that did see something different to the reported story learn not to say what they saw with their own eyes. To do so would cast them out of the herd and in with the 'nutter herd'. We are social animals and being outcast like that is worse than death.
If someone who happens to be sane does relate 'what they saw with their own eyes' to the rest of the herd then it is unlikely that members of the wider herd are going to believe them even if they do not come along with 'moon landings/contrails/whatever' baggage. This is because they are highly invested in the BBC world view and the latitude that it allows. The spectrum will range from Hillary to Trump but not as far as Bernie. Bernie is mainstream, but you get the idea. It is a fixed stage, outside this allowed latitude there will be terrorists and the KKK. The voice of protest will be allowed in this Overton Window with people such as Russell Brand or, in times gone past, Tony Benn. These folk don't have to be 'covert CIA operatives acting as gatekeepers', they just operate within the same Overton Window as everyone else, playing their role quite naturally, the sponges for dissenting voices that don't go along with whomever is in Number 10.
The implications of going with the BBC world view are generally good. You can go on anti-Trump protests posting your pics onto Instagram so everyone knows you are solidly against racism and whatever else it is easy to object to. There is no danger of being cast outside the herd.
The BBC has a veritable 'full spectrum dominance' with radio all around the world, the web as well as their mainstay 'free to air, advert free' television. Britain might not rule the waves any more but the airwaves are doing nicely.
I have not given any incident of where reality and BBC reality differ, however, people that suffered at Hillsborough, people that lived through the miner's strike, people that were there at Bloody Sunday, people that were abused by BBC 'disc jockeys' have had this problem to live with. Due to injustice they have had to 'rebel'. Nobody could speak out about the 'disc jockey' whose name we do not speak of until he died and was buried under six foot of concrete (he knew that his grave would not lay undisturbed). Yet everyone in the BBC knew. And in the wider press. And he was only a 'disc jockey' without any nuclear weapons or henchmen.
Hence, in the UK at least, the BBC is how the government has weaponised 'mind control' and made questioning authority not something one does. People just do not have the mindset to do so as they have been encultured to be British.