It may have been pouring with rain, water overrunning the gutters and spreading fast and deep across London's Euston Road, but this did not stop a queue forming, and growing until it snaked almost all the way back to Euston station. Inside Friends House, a Quaker-run meeting hall, the excitement was palpable. People searched for friends and seats with thinly disguised anxiety; all watched the stage until, about 15 minutes late, a short, slightly top-heavy old man climbed carefully on to the stage and sat down. The hall filled with cheers and clapping, with whoops and with whistles.

Noam Chomsky, said two speakers (one of them Mariam Said, whose late husband, Edward, this lecture honours) "needs no introduction". A tired turn of phrase, but they had a point: in a bookshop down the road the politics section is divided into biography, reference, the Clintons, Obama, Thatcher, Marx, and Noam Chomsky. He topped the first Foreign Policy/Prospect Magazine list of global thinkers in 2005 (the most recent, however, perhaps reflecting a new editorship and a new rubric, lists him not at all). One study of the most frequently cited academic sources of all time found that he ranked eighth, just below Plato and Freud. The list included the Bible.

When he starts speaking, it is in a monotone that makes no particular rhetorical claim on the audience's attention; in fact, it's almost soporific. Last October, he tells his audience, he visited Gaza for the first time. Within five minutes many of the hallmarks of Chomsky's political writing, and speaking, are displayed: his anger, his extraordinary range of reference and experience – journalism from inside Gaza, personal testimony, detailed knowledge of the old Egyptian government, its secret service, the new Egyptian government, the historical context of the Israeli occupation, recent news reports (of sewage used by the Egyptians to flood tunnels out of Gaza, and by Israelis to spray non-violent protesters). Fact upon fact upon fact, but also a withering, sweeping sarcasm – the atrocities are "tolerated politely by Europe as usual". Harsh, vivid phrases – the "hideously charred corpses of murdered infants"; bodies "writhing in agony" – unspool until they become almost a form of punctuation.

You could argue that the latter is necessary, simply a description of atrocities that must be reported, but it is also a method that has diminishing returns. The facts speak for themselves; the adjectives and the sarcasm have the counterintuitive effect of cheapening them, of imposing on the world a disappointingly crude and simplistic argument. "The sentences," wrote Larissa MacFarquhar in a brilliant New Yorker profile of Chomsky 10 years ago, "are accusations of guilt, but not from a position of innocence or hope for something better: Chomsky's sarcasm is the scowl of a fallen world, the sneer of hell's veteran to its appalled naifs" – and thus, in an odd way, static and ungenerative.

To be fair, he has – as he points out the next day, sitting under the gorgeous, vaulting ceilings of the VIP section of the St Pancras Renaissance hotel – not always been preaching to the converted, or even to the sceptically open-minded. "This [rapturous reception] is radically different from what it was like even five years ago, when in fact [at talks about Israel-Palestine] I had to have police protection because the audience was so hostile." His voice is vanishingly quiet as well as monotonal, and he is slightly deaf, which makes conversation something of a challenge. But he answers questions warmly, and seriously, if not always directly – a surprise, in a way, from someone who has earned a reputation for brutality of argument, and a need to win at all costs. "There really is an alpha-male dominance psychology at work there," a colleague once said of him. "He has some of the primate dominance moves. The staring down. The withering tone of voice." Students have been known to visit him in pairs, so that one can defend the other. But it is perhaps less surprising when you discover that he can spend up to seven hours a day answering emails from fans and the questing public. And in the vast hotel lobby he cuts a slightly fragile figure.

Chomsky, the son of Hebrew teachers who emigrated from Ukraine and Russia at the turn of the last century, began as a Zionist – but the sort of Zionist who wanted a socialist state in which Jews and Arabs worked together as equals. Since then he has been accused of antisemitism (due to defending some 35 years ago the right to free speech of a French professor who was later convicted of Holocaust denial), and, as the Nation once pointed out, it is a measure of the limitations discussions of the Middle East have sometimes had in his home country that he at one point acquired the reputation of being America's most prominent self-hating Jew. These days he argues tirelessly for the rights of Palestinians. In this week's lecture he quoted various reactions to the Oslo accords, which turn 20 in September, including a description of them as "an infernal trap". He replied to a question about whether Israel would still exist in 50 years' time by saying, among other things, that "Israel is following policies which maximise its security threats … policies which choose expansion over security … policies which lead to their moral degradation, their isolation, their deligitimation, as they call it now, and very likely ultimate destruction. That's not impossible." Obama arrived in Israel this week accompanied by some of the lowest expectations ever ascribed to a US president visiting the country. There was so much more hope, I suggest to Chomsky, when Obama was first elected, and he spoke about the Middle East. "There were illusions. He came into office with dramatic rhetoric about hope and change, but there was never any substance behind them," he responds.

He seems cautiously optimistic about the Arab spring, which he sees as a "classic example … [of] powerful grassroots movements, primarily in Tunisia and Egypt" – but is dryly ironic about the west's relationship with what is happening on the ground. "In Egypt, on the eve of Tahrir Square, there was a major poll which found that overwhelmingly – 80-90%, numbers like that – Egyptians regarded the main threats they face as the US and Israel. They don't like Iran – Arabs generally don't like Iran – but they didn't consider it a threat. In fact, back then a considerable number of Egyptians thought the region might be better off if Iran had nuclear weapons. Not because they wanted Iran to have nuclear weapons, but to offset the real threats they faced. So that's obviously not the kind of policy that the west wants to listen to. Other polls are somewhat different, but the basic story is about the same – what Egyptians want is not what the west would like to see. So therefore they are opposed to democracy."

What does Chomsky, who has infuriated some with his dismissal of the "new military humanism", think should be done in Syria, if anything? Should the west arm the opposition? Should it intervene? "I tend to think that providing arms is going to escalate the conflict. I think there has to be some kind of negotiated settlement. The question is which kind. But it's going to have to be primarily among Syrians. Outsiders can try to help set up the conditions, and there's no doubt that the government is carrying out plenty of atrocities, and the opposition some, but not as many. There's a threat that the country is on a suicidal course. Nobody wants that."

Chomsky first came to prominence in 1959, with the argument, detailed in a book review (but already present in his first book, published two years earlier), that contrary to the prevailing idea that children learned language by copying and by reinforcement (ie behaviourism), basic grammatical arrangements were already present at birth. The argument revolutionised the study of linguistics; it had fundamental ramifications for anyone studying the mind. It also has interesting, even troubling ramifications for his politics. If we are born with innate structures of linguistic and by extension moral thought, isn't this a kind of determinism that denies political agency? What is the point of arguing for any change at all?

"The most libertarian positions accept the same view," he answers. "That there are instincts, basic conditions of human nature that lead to a preferred social order. In fact, if you're in favour of any policy – reform, revolution, stability, regression, whatever – if you're at least minimally moral, it's because you think it's somehow good for people. And good for people means conforming to their fundamental nature. So whoever you are, whatever your position is, you're making some tacit assumptions about fundamental human nature … The question is: what do we strive for in developing a social order that is conducive to fundamental human needs? Are human beings born to be servants to masters, or are they born to be free, creative individuals who work with others to inquire, create, develop their own lives? I mean, if humans were totally unstructured creatures, they would be … a tool which can properly be shaped by outside forces. That's why if you look at the history of what's called radical behaviourism, [where] you can be completely shaped by outside forces – when [the advocates of this] spell out what they think society ought to be, it's totalitarian."

Chomsky, now 84, has been politically engaged all his life; his first published article, in fact, was against fascism, and written when he was 10. Where does the anger come from? "I grew up in the Depression. My parents had jobs, but a lot of the family were unemployed working class, so they had no jobs at all. So I saw poverty and repression right away. People would come to the door trying to sell rags – that was when I was four years old. I remember riding with my mother in a trolley car and passing a textile worker's strike where the women were striking outside and the police were beating them bloody."

He met Carol, who would become his wife, at about the same time, when he was five years old. They married when she was 19 and he 21, and were together until she died nearly 60 years later, in 2008. He talks about her constantly, given the chance: how she was so strict about his schedule when they travelled (she often accompanied him on lecture tours) that in Latin America they called her El Comandante; the various bureaucratic scrapes they got into, all over the world. By all accounts, she also enforced balance in his life: made sure he watched an hour of TV a night, went to movies and concerts, encouraged his love of sailing (at one point, he owned a small fleet of sailboats, plus a motorboat); she water-skied until she was 75.

But she was also politically involved: she took her daughters (they had three children: two girls and a boy) to demonstrations; he tells me a story about how, when they were protesting against the Vietnam war, they were once both arrested on the same day. "And you get one phone call. So my wife called our older daughter, who was at that time 12, I guess, and told her, 'We're not going to come home tonight, can you take care of the two kids?' That's life." At another point, when it looked like he would be jailed for a long time, she went back to school to study for a PhD, so that she could support the children alone. It makes no sense, he told an interviewer a couple of years ago, for a woman to die before her husband, "because women manage so much better, they talk and support each other. My oldest and closest friend is in the office next door to me; we haven't once talked about Carol." His eldest daughter often helps him now. "There's a transition point, in some way."

Does he think that in all these years of talking and arguing and writing, he has ever changed one specific thing? "I don't think any individual changes anything alone. Martin Luther King was an important figure but he couldn't have said: 'This is what I changed.' He came to prominence on a groundswell that was created by mostly young people acting on the ground. In the early years of the antiwar movement we were all doing organising and writing and speaking and gradually certain people could do certain things more easily and effectively, so I pretty much dropped out of organising – I thought the teaching and writing was more effective. Others, friends of mine, did the opposite. But they're not less influential. Just not known."

In the cavernous Friends' House, the last words of his speech are: "Unless the powerful are capable of learning to respect the dignity of their victims … impassable barriers will remain, and the world will be doomed to violence, cruelty and bitter suffering." It's a gloomy coda, but he leaves to a standing ovation.

• This article was amended on 23 March 2013. The original said that Chomsky had been accused of antisemitism due to defending the right to free speech of a French professor who espoused such views. To clarify, the professor was convicted of Holocaust denial. The article was further amended on 24 March 2013 to clarify an incorrect reference to Chomsky having been called "America's most prominent self-hating Jew". The error was the result of a quote being misconstrued.