not baking a cake by default means they're not providing any material support/not involved with something they object to
they can, as a business or company, endorse whatever they want within reason... campaign for issues, chose to not campaign for other issues - oppose issues etc...etc... You get to chose what you will and won't produce etc..
you could equally say that a wedding photographer's job is to take the pictures and produce them as the couple want - but we've already heard from one wedding photographer in this thread who simply won't allow say selective colouring because he doesn't like it - that's simply his choice in dictating what he is and isn't prepared to create
It's not really providing material support or facilitating a campaign, they are baking a cake. I don't think bakeries values should be on political campaigns but rather baking cakes and setting aside everything else. It's not like the cake would have been shown off, from so and so's bakery, they are in support of our campaign. Rather here's a cakes and here's our message. They are in no way shape or form linked together. Would the bakery be happy to produce anti gay cakes? if so they would then be discriminating by not offering the same cakes to pro gay people.
I don't think comparison with the photographer is comparable since clearly the baker offers the service to begin with aka writing messages and images, where as the photograph fro the onset doesn't offer the service. It would be comparable if the photographer didn't allow certain colourings to some peoples photos and on others.
OK so as a Muslim would you happily make a cake stating 'Jesus is the son of God' for a Christian group?
Up to this point no issue, its not my beliefs. Just like if I ran a printing service and a client asked me to print bibles. I'm not endorsing the bible or its teaching, I just print stuff.
What about if it included a picture of Jesus (so a picture of a prophet...)? I'd presume that lots of Muslims would object to the second and quite a few would object to the first too... and they'd have every right to.
That would be something a Muslim could not do by action, difference is that would be across the board rather than selective. It is not endorsing or facilitating, simply something they couldn't do irrespective of the client.
You can't oblige someone to create something they don't believe in. It doesn't have to be hateful... such a cake isn't in itself but it also goes against the beliefs of another group of people.
Writing someone's text wouldn't fall in to that category, it wouldn't go against your belief in writing since your writing someone else's belief.
Sure maybe some Muslims could create the first cake and argue that they're just making the cake and don't agree with the message.... but then again gay marriage is controversial for some Christians - rightly or wrongly they see it as something that is wrong, is 'sinful'.... Maybe baking this cake for the baker is like a Romanian printer being asked to print some UKIP fliers...
They believe gay marriage is wrong, not writing text for someone else's belief of gay marriage which has nothing to do with you unless the word "gay" was forbidden to be drawn out hence why the picture comparison isn't really viable within these boundaries.
No doubt it's a tricky one, it would be hard for anyone to sit on either side of the fence and say what's wrong and right. Nor do I believe the bakery should be punished.