Transgender issues have become the latest free speech battleground. A letter to last Sunday's Observer expressed alarm at attempts by some trans activists to ban their feminist critics from speaking at universities and other institutions. It was signed by over 100 left-wing, feminist and human rights activists, including myself.

The letter cited attempts to ban Germaine Greer, Kate Smurthwaite and Julie Bindel. It noted:

"No-platforming used to be a tactic used against self-proclaimed fascists and Holocaust-deniers. But today it is being used to prevent the expression of feminist arguments critical of the sex industry and of some demands made by trans activists.

"The feminists who hold these views have never advocated or engaged in violence against any group of people. Yet it is argued that the mere presence of anyone said to hold those views is a threat....You do not have to agree with the views that are being silenced to find these tactics illiberal and undemocratic."

I disagree with the trans and sex work stance of some feminists. I did not draft the letter and would have worded it differently, with a robust defence of the human rights of trans people and sex workers. However, despite the letter's imperfections, I concluded that the defence of free speech outweighed my reservations. I signed the letter, somewhat reluctantly.

I accept that some trans people, having suffered a lifetime of victimisation compounded by the negative views of several leading feminists, were upset by the letter. But it was never my intention (or that of other signatories, as far as I know) to offend trans people or cause them distress. I am sorry if this is the way some of them feel about the letter and my name on it.

\'I did not draft the letter and would have worded it differently, with a robust defence of the human rights of trans people and sex workers.\'

For me, free speech is one of the most precious of all human rights. It is the foundation of a democratic, open society. It should be defended without exception, unless it involves threats, harassment or incitements to violence.

The most effective way to defeat bigoted ideas is not by proscription but by challenging and exposing them - and by presenting better, non-bigoted ideas. That's why I've often accepted invitations to debate homophobes, misogynists, transphobes and anti-Muslim zealots. The feedback I've received nearly always suggests that they've come out of such debates damaged and discredited.

This was the case when I did a BBC Radio 4 debate on trans issues against Julie Bindel many years ago. Trans activists say she's transphobic and should not be given a platform. As a result, she's been banned from speaking at some universities, even on non-trans issues (the latter exclusion seems particularly excessive).

But far from gaining from the platform she was given, Bindel emerged from the BBC debate with much of the audience rejecting her point of view. This experience confirmed to me that exposing transphobes in debates is more effective than no-platforming them, as well as being more democratic.

We weren't demanding carte blanche for feminist trans opponents

The appeal for open debate, rather than censorship, was the gist of the Observer letter. It seemed a reasonable point to make: that a minority of trans activists are using the same no-platform tactics against trans critics that were once used to silence trans people. Double standards?

In their defence, trans campaigners say that free speech does not oblige anyone to give anti-trans feminists speaking engagements or media time. Quite true. Not being invited to speak is not necessarily the same as being banned. Our letter was not demanding that every institution must give a platform to feminists critical of aspects of the trans agenda. It was focussed on instances where there were attempts to get a person blocked or withdraw their invitation.

When I signed, I had no inkling of the gigantic hostile Twitter storm that would break within an hour of publication last Saturday morning and continue non-stop for three days.

Although used to being assailed and vilified, I was stunned by the vicious and often untrue nature of the Twitter attacks - and by the sheer volume. A colleague estimates that I received 4,000 to 5,000 mostly hostile comments from Saturday to Monday. They ran from 8am to midnight, continuous and relentless. At peak times, there were 30-40 comments a minute.

Some were fine: critical but polite and fair. Many were hateful and abusive: homo, foreigner, misogynist, paedophile, nutter and so on. Others were threatening: "I would like to tweet about your murder you f*cking parasite."

Most tweets completely misrepresented what the letter said and my personal record of support for trans people for over four decades. It is one of the largest and most vituperative onslaughts in my 48 years of human rights activism.

Full text of the Guardian letter The fate of Kate Smurthwaite's comedy show, cancelled by Goldsmith's College in London last month ("What could be more absurd than censorship on campus", Nick Cohen, Comment) is part of a worrying pattern of intimidation and silencing of individuals whose views are deemed "transphobic" or "whorephobic". Most of the people so labelled are feminists or pro-feminist men, some have experience in the sex industry, some are transgender. Last month, there were calls for the Cambridge Union to withdraw a speaking invitation to Germaine Greer; then the Green party came under pressure to repudiate the philosophy lecturer Rupert Read after he questioned the arguments put forward by some trans-activists. The feminist activist and writer Julie Bindel has been "no-platformed" by the National Union of Students for several years. "No platforming" used to be a tactic used against self-proclaimed fascists and Holocaust-deniers. But today it is being used to prevent the expression of feminist arguments critical of the sex industry and of some demands made by trans activists. The feminists who hold these views have never advocated or engaged in violence against any group of people. Yet it is argued that the mere presence of anyone said to hold those views is a threat to a protected minority group's safety. You do not have to agree with the views that are being silenced to find these tactics illiberal and undemocratic. Universities have a particular responsibility to resist this kind of bullying. We call on universities and other organisations to stand up to attempts at intimidation and affirm their support for the basic principles of democratic political exchange.

It prompted me to tweet: "Today's #trans twitter storm about a letter has provoked more responses than any of my tweets about the MURDER of trans people. Priorities?" This just provoked more hostility. Some replied: We never asked you to tweet about trans murders (as if I am only permitted to tweet when they ask me to). And: We are tweeting about these killings and don't need your help.

Oh dear. Why reject and alienate allies? Surely a tiny minority like trans people need non-trans supporters to win the rights they seek?

I couldn't win whatever I said. If I did not support trans issues I would be accused of prejudice and neglect. When I did support them, I was condemned for uninvited interventions and disempowering trans campaigners.

My solidarity with trans people began in the early 1970s when most people ignored or opposed trans rights. At the weekend, some critics told me that my backing for the trans community is condescending, fake, patronising and not wanted; that I am attempting to dictate, hijack and dominate the trans agenda.

These naysayers claim to represent the trans community but I doubt they do. I suspect they are a small vociferous minority of trans people and non-trans allies.

Gratifyingly, I have received messages of support and commiserations from some trans activists. They understood that the Observer letter was about free speech, not an assault on trans rights and campaigners.

Nevertheless, there were plenty of people who accused me of "attacking" the trans community; claiming that I "advocate for our oppressors' voices over our own." That's nonsense. The letter did not defend the views of anti-trans feminists. It contained no attacks on trans people or trans equality.

Some critics said that, by signing the letter, I have sided with anti-trans bigots and am complicit with "opinions [that] lead to [trans] people getting killed." ​The suggestion that our calm, temperate letter will provoke anti-trans hate and violence is absurd.

\'I have received messages of support and commiserations from some trans activists. They understood that the Observer letter was about free speech, not an assault on trans rights and campaigners.\'

I have not endorsed any anti-trans opinions. I simply defended free speech for feminists who I disagree with, which is what genuine freedom of expression is all about. ​

Others condemn me for "knowingly" co-signing with "notorious transphobes." Not true. When I was asked to sign up, I was not aware of who else would add their names. Yet I am now being condemned via the McCarthyite tactic of guilt by association.

Regrettably, a crucial sentence in the letter was cut, for space reasons, without my knowledge or agreement. It read: "Some of us have disagreements with the views expressed" (by feminist critics of trans people). I was not happy about that cut because the deleted words made it very clear that some of the signatories are strong trans allies and advocates.

Another rebuke was that the letter was an attempt to "silence" trans people. This is pure fabrication. The letter opposed attempts to silence feminist critics of trans people, not the other way around.

Trans activist and former Cambridge City councillor Sarah Brown was one of many people who alleged that the letter writers wanted to stop protests against "trans oppressors." She tweeted: "You signed a letter castigating members of discriminated-against minorities for exercising their right to protest." No Sarah. The letter was not against protests. It was against bans and censorship. I've supported pickets against transphobes, including against anti-trans feminists.

Another criticism was that I am a privileged, white, non-trans man and therefore have no right to an opinion. As I replied: "I am the son of a factory worker. I left school at 16 to help support my family. Some privilege!" This just provoked further abuse and ridicule.

A few people accused me of hypocrisy because I have supported the banning of extremist clerics and 'murder music' reggae singers. But this was not because they were merely homophobic. It was because they advocated the killing of gay people; thereby crossing the red line of incitement to violence.

Despite being burned by zealots in the twittersphere, nothing has changed. I always have and always will support free speech and the human rights of trans people and sex workers.

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