That was the issue before the appeal court in Belfast in the notorious “gay cake” row.
It ruled that the Christian-owned Ashers Bakery acted unlawfully when it refused to decorate a cake with the message: “Support gay marriage.”
The judges have decided, in effect, that businesses cannot lawfully refuse a customer’s request to promote a message — presumably even if it is sexist, xenophobic or anti-gay and even if the business owners have a conscientious objection to it.
The verdict is a setback for freedom of expression — a dangerous, authoritarian precedent.
As well as ruling that Ashers can be legally penalised for not aiding the promotion of same-sex marriage, it also implies that gay bakers could be at risk of legal action if they refuse to decorate cakes with homophobic wording.
It gives a green light to far-right extremists to demand that businesses facilitate the promotion of their anti-immigrant opinions.
Do we really want a Muslim printer to be legally obliged to publish cartoons of Muhammad and a Jewish printer to be required, under threat of legal action, to publish a book propagating Holocaust denial?
Despite disagreeing profoundly with Ashers’ opposition to marriage equality, in a free society neither they nor anyone else should be compelled to facilitate a political idea they oppose.
Ashers did not discriminate against the customer who ordered the cake, Gareth Lee, because he was gay. They had served him previously and would do so again. Their objection was to the message he wanted on the cake.
Discrimination against LGBT people is wrong and is rightly unlawful.
But in a democratic society, people should be able to discriminate against ideas they disagree with.
Unlike the court, I err on the side of freedom of conscience, expression and religion.
While Christian bed-and-breakfast owners and civil partnership registrars were wrong to deny service to gay people, this case is different.
It is about the refusal to facilitate an idea — namely, support for same-sex marriage.
Discrimination against people should be always unlawful but not discrimination against ideas and opinions.