Just a thought, but what's to stop them buying a generic cake and putting the Queerspace logo on it themselves? I'm assuming that was the only decoration missing?
They could probably have asked for, and received, a rainbow cake with unicorns on it (cliches ahoy). It was just the name of that political group that was the problem?
It was the 'support gay marriage' slogan that was what the baker objected to being associated with. They could have bought any cake they wanted if it was apolitical.