Gay and lesbian rights activists are seeking to be the new "moral enforcers" and it is Christian religious conservatives who now need protection for their right to express dissent against "the new orthodoxy", the Court of Appeal was told today.
Core Issues Trust, a Christian charity, is challenging a ban on its London bus advert suggesting gays can be helped to ''move out of homosexuality''.
The ad posters designed for the sides of the capital's buses read: ''Not Gay! Ex-Gay, Post-Gay and Proud. Get over it!''
The ad was a response to a bus poster campaign by gay rights group Stonewall, which carried the message: ''Some people are gay. Get over it!''
Paul Diamond told three appeal judges at the heart of the case was the "ironical" situation in modern British society where ancient Biblical scriptures, which played an important role in forming the nation's morals, were now in danger of containing views which could no longer be expressed "in a land with a reputation for free speech".
Mr Diamond said the Bible and it Christian scriptures only permitted sexual relationships between one man and one woman in marriage and people should be entitled to express that view.
He said the case raised the question: "Is the belief that homosexuality is a sin worthy of respect in a democratic society?"
The charity accuses London mayor Boris Johnson of unlawfully using his position as chairman of Transport for London (TfL) to obtain the TfL ban of the Christian ad in order to secure the gay vote and advance his 2012 re-election campaign.
High Court judge Mrs Justice Lang rejected the claim in March and ruled: ''In my view, such unlawfulness has not been established on the evidence.''
Mr Johnson said the Core Issues ad was ''offensive to gays'' and said it could lead to retaliation against the wider Christian community.
Mr Diamond is arguing on appeal that an "email trail" not disclosed by the Mayor's office at the High Court, and discovered later following a Freedom of Information request by the trust, supported its claim over Mr Johnson's role in banning the ad.
The trust says its works with gay people seeking to change their lifestyles, but rejects the idea of offering a gay cure.
It is asking the appeal judges to uphold its right to freedom of expression under Article 10 of the European Convention on Human Rights, which it says has been violated by the ban.
It is also relying on Article 9, which protects the right to freedom of thought, conscience and religion.
Mrs Justice Lang ruled TfL's decision-making process "fell below the standards to be expected of a responsible public body,'' but the trust's Article 10 rights were outweighed by the rights of gays to respect for their private and family life under article 8(1).
The judge said TfL was legally justified in imposing the prohibition in the run-up to the mayoral elections in May 2012 because the ad would cause ''grave offence'' to gays and ''increase the risk of prejudice and homophobic attacks".
TfL was also under a duty under the 2010 Equality Act to eliminate discrimination and harassment against gays and to ''foster good relations, tackle prejudice and promote understanding''.
The judge declared: ''Displaying the advertisement would have been in breach of that duty.''
Asking the appeal judges to overturn her decision, Mr Diamond argued there was "nothing aggressive" in the message of the Core Issues ad.
"We were simply trying to engender a debate. There is a debate out there - it is not all one way. People don't have the same views. There is an alternative."