IN his final decade, I was lucky enough to be one of Terry Wogan’s occasional lunching companions.

These were titanic occasions: just the two of us, heroic servings of food, industrial quantities of alcohol, weapons-grade gossip. Terry had met absolutely everyone who mattered through the second half of the 20th century, and was a conversational conveyor belt of hilarious and sometimes eye-popping anecdotes. For all his genuine charm and bonhomie, though, he didn’t suffer fools. His judgments were sharp and could be acidic.

He had spent his life at the BBC, and was particularly cutting about two groups there: the new generation of managers who, as he saw it, understood nothing but spreadsheets and organograms, and the young, highly-paid “celebrities” who had risen to instant prominence without paying their dues. But for the most part he maintained a deep love of the organisation.

“The BBC is the greatest broadcaster in the world,” he once said. “It’s the standard that everyone measures themselves against. If we lose the BBC, it won’t be quite as bad as losing the Royal Family, but an integral part of this country will have gone. But then, I’m an old guy.’

Old guy or not, he was, as usual, spot on. For all its flaws, its bureaucratic ponderousness, its infuriating largesse with the public’s money, its corporate overreach, the BBC is still worth it. It remains, nearly a century since its creation, a fantastic idea: a commonly-owned project to “inform, educate and entertain” for the purposes of the public good. It is, arguably even more than the Royals, the single most effective contributor to Britain’s soft power, an internationally recognised symbol of truth-seeking, artistic craft, journalistic courage and global engagement. That’s not to say its private sector competitors don’t often match or even surpass its efforts, but only the BBC does it all so well, so consistently, as a statement of civilised, collective, national intent. Not the least of its attractions might be that it helps keep the rest honest. The BBC’s existence speaks well of us.

Like every branch of the mainstream media, it has struggled to cope with the rapid rise and transformative impact of digital technology. Journalists like me always grumble about the damage its extravagantly-funded and lavishly-staffed free website has done to the prospects of national and local newspapers in this difficult new online climate. The argument that the BBC tries to do too much and should focus on a tighter set of priorities is, I think, well made. The licence fee in its current form will only come to look ever more anachronistic as the years go on.

Social media has handed the corporation’s most vitriolic critics the equivalent of a megaphone as well as the ability to create and sustain frenzied campaigns against its supposed “bias”. It’s no coincidence that these groups are the same ones that have turned Twitter and Facebook into such toxic sewers: the Cybernats, the Ukippers and the Corbynistas. These strange little gangs, their strings pulled by cackling political Svengalis, are fired by a misplaced sense of their own moral righteousness, enraged by perceived injustices and slights, are wholly without perspective, balance or any grasp of nuance.

For this reason, it’s no surprise the BBC drives them potty. It is everything they are not: deliberately impartial, painstakingly measured, minded to interrogate issues from every side. It tries to avoid easy judgements and casual slander. That’s not to say it always succeeds, or that it doesn’t make bad decisions and stupid mistakes, but such lapses are usually the result of ignorance rather than malice.

Here’s the problem: it’s one thing for Alex Salmond’s barmy army to turn up outside Pacific Quay with massive banners demanding the head of Nick Robinson, or the unhinged hard Left to spend weeks complaining about the non-existent photoshopping of Jeremy Corbyn’s hat on a Newsnight backdrop, or for hardcore Leavers to insist various BBC presenters are Remain shills – we expect nothing less from conspiracy theorists and cranks. They are all a mirror of each other.

It’s quite another, however, for those who make a claim to moderation and considered practicality to adopt similar tactics. It has been bizarre to watch the usually sensible Lord Adonis turn his guns on the BBC in recent weeks. He has badgered away on social media to the point of obsession, and has begun using the hashtag #BrexitBroadcastingCorporation. He has singled out individuals for criticism who aren’t in a position to argue back. Yesterday, he tweeted: “Vital to understand that the BBC is now part of the problem not the solution. It was taken over by the Brexiters c.2014…It is 2/3 of the way towards Fox News & fake news.” I have a great deal of respect for Lord Adonis, but there is only one word to describe this view: bananas.

He has been joined in this unpleasant endeavour by Alastair Campbell, Tony Blair’s former spin doctor and a long-time critic of the media, and by some newspaper columnists who should know better. They have adopted the pathology of the fringe and - perhaps unknowingly - are risking their personal credibility in the process. Is the BBC anti-Brexit as Leavers claim, or pro-Brexit as the Adonis crew argues? It can’t be both, can it? So is it possible it’s neither, and that those flitting shapes the critics keep seeing in the corner of their eye don’t really exist?

All of the UK’s major institutions have taken a kicking in the past decade or so, and usually with good reason. The BBC has not escaped, and from its over-inflated salary payments to its poor handling of child abuse allegations has deserved the brickbats. There are some very real and serious debates to be had about its future scale and shape.

But its core purpose is now being repeatedly called into question - its contribution to the public good, its focus on truth-seeking, its reliability as a fair-minded player in the public realm. And not just by those on the political extremes but by those who otherwise claim to be sober-minded, judicious and mania-free. I confess myself baffled. Why play into enemy hands by slashing away at the case for the BBC’s very existence? How do they think this ends? Were he here to give it, Terry Wogan’s judgement on them would, I suspect, not be gentle.