The High Court violated an important principle of free of expression when it ruled today that Transport for London was justified in banning "ex-gay’ adverts on London buses.

The decision has been welcome by the gay lobby group Stonewall, but not by me.

I agree that the bus adverts - promoted and defended by fringe Christian groups - were homophobic and offensive. They insinuated that gay people can be cured of their homosexuality. This is untrue and misleading. However, the language of the adverts was not abusive, menacing or threatening.

On balance, on the grounds of free speech, the adverts should not have been banned.

In her ruling, the judge, Justice Lang, seemed to accept the suggestion that the wording risked increasing public prejudice and hate crime. This is doubtful.

The banned adverts on London buses read: "Not Gay! Ex-Gay, Post-Gay and Proud. Get over it!"

The advert wording was not intemperate or inflammatory. It was wrong but polite. It was not stated in terms that would easily excite hostility towards lesbian, gay, bisexual and transgender (LGBT) people.

The organisation that placed the adverts, Core Issues Trust, promotes the false idea that gay people can turn straight.

However, the adverts did not directly make this claim.

I disagree with the gay conversion therapies of the Core Issues Trust. I think they cause harm. They delude vulnerable LGBT people and give them false hope that they can change their sexual orientation. The ex-gay prospectus is false.

I have recently challenged the ideas and methodology of the Core Issues Trust, and will continue to do so - using reason, logic and empirical evidence to refute their claims.

Core Issues Trust is hypocritical. It would never demand or defend a similar message directed at the black, Jewish or disabled communities, urging them to disavow their identity and heritage. Such a message would rightly provoke public outrage. So why are the Core Issues Trust and their Christian fundamentalist supporters - like Christian Concern and the Christian Legal Centre - pushing this message to the LGBT community? It looks two-faced.

Justice Lang made her decision to uphold the advert ban on the grounds that they were gravely offensive to gay people. She is right. They are offensive but being offensive is not a legitimate basis for banning anything.

In a free society there is no right to not be offended. Almost anything that anyone says can potentially be deemed offensive by someone. The law should not cater to the sensitivities of any section of the public. If it did, many adverts, plays, books and films would be banned.

Given that Transport for London allowed Stonewall’s advert - "Some people are gay. Get over it!" - it seems double standards to ban the counter message of the Core Issues Trust.

Banning these adverts reminds me of the bad old days when gay advertisements were banned on the grounds that they were offensive. For decades, LGBT helplines, youth groups and campaign organisations faced bans on advertising their services.

It is not right for the LGBT community to turn around and adopt the oppressive, anti-free speech tactics of our past oppressors.

>Free speech is one of the most important of all human rights. It should only be limited in extreme circumstances, such as when people abuse it to incite violence or harass and intimidate others.

Free speech is for everyone - even those with whom we disagree.

Peter Tatchell is the director of the Peter Tatchell Foundation