Carl Bernstein wants me to read something first. Fortunately it's not All The President's Men – where you can remember the story, but not perhaps every last detail – but instead an article he wrote in 1992 called The Idiot Culture, which is helpfully republished on his website. It's a densely argued four-page piece, which concludes "the media are probably the most powerful of all our institutions today; and they are squandering their power and ignoring their obligation".

One hesitates to summarise though, not least because Bernstein is wary of simplification. His answers to questions are lengthy, nuanced, and he likes to emphasise the importance of "context". But he thinks the 1992 article, written before the rise of Murdoch in the US, Fox News and phone hacking, particularly relevant today, as it describes the dominance of talk-show journalism and celebrity-driven news or, as he puts it, "the spectacle and the triumph of the idiot culture".

He is in London this week, to participate in a Guardian-organised debate entitled After Hacking: How can the press restore trust?, and if anybody can decide if hackgate (more of that later) has any parallels to Watergate, Bernstein is one of the few who can do it legitimately. In fact, he has made the link already, in a 9 July article published on the Daily Beast and Newsweek, called Murdoch's Watergate.

At first, though, Bernstein is reticent about being drawn into the topic for this interview, saying, "look what I wrote in that piece". He says that he wants to save fresh thinking on the topic for his visit to the UK. But he returns to theme later on, pointing out that the hacking story "was the first time I made comparisons between another event and Watergate".

In its way it is significant. The parallel, as he sees it, stems from the fact that Rupert Murdoch "in Britain captured to an incredible extent the press, the police and political institutions", and that has been followed by "a mad search for a smoking gun to implicate Murdoch in a definite manner to a particular act" of hacking "like in Watergate". Murdoch, on this thinking, is Richard Nixon.

"Hacking is about a notion of what journalism is and what is permissible – just as Watergate was about what it's permissible for the president to do," he says, arguing that Murdoch is, in the broadest sense, responsible for his now closed Sunday tabloid. He describes the News of the World as "a reflection of the man who presides over that empire" – which is a way to describe the conduct of those who worked for Nixon too.

Yet, elsewhere in our conversation Bernstein's verdict on Murdoch is more mixed. When we first talk about him, he says "it's important not to be unfair to Murdoch" because "he's the most far seeing media entrepreneur of our time". There is qualified praise for the Wall Street Journal and the Times where "an awful lot of people in those institutions try to produce the best available version of the truth" – Bernstein's phrase for the true journalistic undertaking – and the observation that "Murdoch put The Simpsons on air", which appears not be a criticism because the man whose News Corporation owns Fox film and television also "showed he could understand the information consumer".

But finally, there is this verdict: "Some of his newsrooms showed such disregard for any semblance of reasonable privacy and even the law, and this had an effect on other newsrooms on both sides of the Atlantic".

This is characteristic of Bernstein's approach to thinking; pros and cons weighed up before conclusions drawn. Ask him if he believes the US is still in the grip of the idiot culture, and he responds by heaping praise on the New York Times – "the best English-speaking newspaper, better than it has been for years" – and says his alma mater, the Washington Post, is still "a source of some great reporting, particularly in the field of national security".

But he is highly critical of local television news, which is "just plain qualitatively lousy", and argues that network news has lost its way to cable news, which is in turn dominated by Fox News. Fox, he says, provides "quote news unquote" by which he means the channel plays to viewers' "already held ideological bias" rather than trying to investigate and establish "the best available version of the truth" again. For Bernstein, though, that doesn't mean journalists should try to aim to "to give equal time to one side and the other" as an alternative to the Fox approach because the idea that there can be two equally correct points of view on a topic is "demonstrably false and indeed crazy". In short, there are right answers.

It won't, then, come as a surprise that Bernstein believes in long-form journalism. He may be at pains to stress he is no Luddite, but nevertheless he is not on Twitter, although "I look at it sometimes". His style is to "think about what something means" rather than pump out a quick thought. "Even doing a blog still doesn't appeal," he says, before namechecking Hendrik Hertzberg in the New Yorker, and Andrew Sullivan's Daily Dish as bloggers he follows.

Bernstein's work, he says, focuses on "primary projects" – which include work on a "largely fictional" film with director Steven Soderberg, which "has political overtones, but goes way beyond politics", and a TV series for an unnamed cable network "about the US Congress" on which he has been working, apparently, for four or five years. That job, he says, will be done in 18 months, which is the epitome of the non-Twitter project.

More tantalisingly, though, is work on an early memoir. When Bernstein was 16 he became a copyboy at the Washington Star, which served as his university education, becoming a reporter at 19. It was the early 1960s, and he recalls that he had to "attend almost all of Kennedy's press conferences" to help check quotes. On the day Kennedy was assassinated he had to dash off "to Capitol Hill to find the Speaker of the House hiding under a desk". Here were the journalistic underpinnings of the relatively junior Washington Post reporter, who teamed up with Bob Woodward between 1972 to 1974 to produce a string of stories that brought down a president.

"FBI Aides find that Nixon Aides Sabotaged Democrats" with "a massive campaign of political spying", reads one key story from October 1972. Bernstein reflects: "Here's the thing about Watergate: it was the last time the systems in our country worked. The press did its job; the supreme court held that no president was above the law … Congress left no stone unturned."

Now seems the time to ask if the rest of his career has been a let-down (there have been less well remembered books on Pope John Paul II and Hillary Clinton since), and he sort of agrees.

"You'd have to say absolutely, because of what happened, because of how the story was received, was acted upon and is in the legacy of the political culture," which is a hard point to argue with, but a serious way to end a conversation. So I ask, what does he think when people add the suffix gate to even the mildest of scandals.

In a way it disappoints him because "Watergate was incomparable" but he sees it has a popularising purpose too. "Yes I also understand it," he adds, suggesting that the prevailing culture is, at least, not always completely idiotic.