Now a judge has decided Ashers Bakery was wrong to decline the sale.
Director of the Evangelical Alliance in Northern Ireland, Peter Lynas, told Premier: "We think this has far reaching consequences. It'll be concerning for lots of businesses, not just those run by Christians.
"It turns out the customer is always right, and that a business has no discretion in deciding what goods it supplies."
Peter Ould is a Church of England priest and commentator on issues of sexuality. He told Premier: "Here we have, once again, a defence team trying to make this religion versus sexuality and failing.
"I think we really need to reflect upon that, whether there are actually better ways to defend a Christian in court on these kinds of issues."
DUP MLA Paul Givan, who is proposing a "conscience clause" said the ruling was "an attack" on people of faith.
"What we cannot have is a hierarchy of rights, and today there's a clear hierarchy being established that gay rights are more important than the rights of people to hold religious beliefs," he added.
Michael Wardlow, from the Northern Ireland Equality Commission which brought the case, said: "I very much welcome the judgement and I think it sends out a signal confirming the law as we understood it.
"It actually says to people who take part in commercial enterprises that they must act within the anti-discrimination framework."
Robin Allen QC spoke on behalf of Gareth Lee, the man who tried to buy the cake: "He's very glad that the case is now finished and the result vindicates the decision he made to seek the support of the Equality Commission.
"Mr Lee will be making a decision as to where he will be making a donation to charity out of the damages award in due course."
Northern Ireland Deputy First Minister Martin McGuinness tweeted: "Ashers bakery judgement a good result for equality, gay people have for far too long been discriminated against. We and the law on their side."
Malachy O'Hara from gay support group Rainbow Project told Premier's News Hour Ashers hasn't been consistent in its objections.
"Ashers provide a cake decorating service, which they're quite renowned for.
"They have provided a whole variety of different decorations on their cakes before including some which others may claim go against their Christian principles.
"So Halloween cakes, marriage cakes, cakes for Christenings etc, sacraments or religious understandings that may not exactly fit with their brand of evangelicalism."
Peter Ould speaking to Premier's Marcus Jones:
Peter Lynas speaking to Premier's Hannah Tooley:
Malachy O'Hara speaking to Premier's Des Busteed: