This weekend will see the 40th anniversary of the Pride march, but has it lost its radical roots? As the chairman of the London event resigns after last-minute cutbacks, human rights campaigner and organiser of the first Pride, Peter Tatchell, talks to disillusioned marcher Julie Bindel. Oliver Laughland listens in.

Peter Tatchell: My most memorable Pride was Britain's first one, in July 1972. I helped organise it and we had no idea what to expect. We were surprised to have 700 people turn up, but not surprised to be subject to heavy-handed policing. The reactions of the public were an eye-opener: about a third were overtly hostile – we got pelted with beer cans and coins, but the majority of onlookers seemed just confused and bewildered to see so many openly gay people declaring their sexuality and marching for freedom.

Julie Bindel: I attended my first when I was 16, in 1978. I was brought by a friend who was quite a bit older than me. I was overwhelmed to see people displaying their joy with other lesbians and gay men together in a way that, even when onlookers were shouting with rage, we felt completely safe. It was the first sense of how good it was to not have a label of "normal" attached to you. I didn't understand at the time how political it was. That the people on that march weren't just saying: "We can't help it, we were born this way – feel sorry for us."

PT: Some of the slogans we shouted were particularly memorable: "2, 4, 6, 8! Gay is just as good as straight! 3, 5, 7, 9! Lesbians are mighty fine!" These were revolutions in consciousness, which went against the grain of virtually all of human history that designated queers as bad, sad and mad.

JB: I remember a brilliant slogan carried by a lesbian that said: "Don't shout at me fella, your wife's in here!" – so irreverent and unapologetic. It wasn't: "Please accept us" – it was radical and it was in your face.

PT: One belligerent man shouted: "Aren't you ashamed?" To which everyone shouted back in chorus: "No!" and half of us just blew him a kiss. He was gobsmacked.

Oliver Laughland: Is there a particular moment, Julie, that made you lose interest?

JB: Until the early 1980s I had always been delighted to be there. But many lesbians grew rightly critical of some of the lifestyle choices and political views of gay men. We felt that it didn't represent our own oppression. It became about sexual hedonism, and we wanted to march around liberation, rather than just saying "this is just one great party all about sexual access to as many other men we can secure". We felt that issues some gay men were supporting under the rainbow alliance were in opposition to us. We started to march separately. It wasn't a march any more, it was a parade, and it was taken over by the rollerskating nuns and the men with their backsides hanging out. All great street-party stuff, but it had stopped being a political event. But you still go on it every year don't you, Peter?

PT: I've been on every single Pride London for the past 40 years. Nowadays there are only a handful of people carrying political banners. I think overall there has been a dumbing down of the LGBT agenda. That first pride march was organised by the Gay Liberation Front, which had an agenda for social transformation and sexual freedom for everyone, including straight people. We had a critique of mainstream society and culture – it wasn't queers who had to change, but society. Homophobia was the problem, not homosexuality.

JB: I know exactly what you mean. Especially when gay relations are illegal in over 30 countries.

PT: Nearly 80 actually. And more than half are members of the Commonwealth.

OL: You share the same criticism, but you've taken different paths. What is it that still draws you there, Peter?

PT: It's important to maintain the political presence and voice at Pride. I always go with a political message. Last year I carried a placard mocking Nick Griffin …

JB: But Peter, do you think if we didn't have Pride this year, would it really affect our movement, our struggle? Would it make a difference to what we're trying to achieve? I don't think it would. I think we need to replace it with something that goes back to our roots. It's now rotten to the core.

PT: To some extent I think you're right, but even despite the trend towards depoliticisation and commercialisation, the organisers have striven to give it a human rights dimension. There have always been human rights speakers at the rally in Trafalgar Square.

JB: But do people listen? Do they want to hear stories that are painful for any of us to digest when they have just been sinking six Bacardi Breezers and dancing to Madonna on a float? I agree we all have to have fun, parties are fabulous, I've had the best fun as a feminist and a lesbian at similar events, but to me it's a total clash of culture – the politics and the hedonism.

PT: I think some people appreciate these human rights messages. In recent years most of the human rights speakers have had thunderous applause.

JB: The last Pride I was on it looked like I was on a building site. Some gay culture has geared towards the cult of machismo like nothing else. That makes a lot of women very uncomfortable on gay Pride. It's only dressing up, but it's the insignia of our oppression.

OL: Do you see Pride as a fundamentally conservative and mainstream event now, Julie? This is the criticism levelled at the movement for gay marriage, too.

JB: David Cameron said: 'I don't support gay marriage in spite of being a conservative, I support it because I'm a conservative' – never a truer word has been said. It is the most conservative struggle we could adopt. But while I'm critical of us wasting time on it – hasn't it brought the nasty, bigoted homophobes out of the woodwork, too? I think Pride has become both wildly hedonistic and a deeply conservative movement, with its message of "please tolerate us". I don't want tolerance, I want liberation.

PT: I absolutely share your feminist critique of marriage. I would never personally want to get married. I think it's a deeply heterosexist institution. But as a democrat, I defend the right of people to make the misguided choice to get married, if that is what they wish. I want the right to get married, precisely so I can have the freedom to reject it. The campaign for same-sex marriage is fundamentally conservative at one level, while being profoundly radical at another. So I say, join the fray, expose and challenge and defeat these people who would, if they had half a chance, keep us down for ever and a day!

JB: I want people to look at the Pride procession and feel uncomfortable and be challenged by it. I want them to be faced with something every year that stops the traffic and inconveniences them, because they might stop to think about why we march through the streets. Then I would definitely start going on Pride again.