Celebrating a wedding is not offensive. If a business owner thinks otherwise and wants to discriminate on the basis of his beliefs then he’s the one who’s got a problem. He can have those beliefs all he wants but he should not be allowed to use a business to project that prejudice in public. Why? Because it’s rightly against the law to discriminate in a public setting on the basis of race, gender or sexuality. You can’t refuse a service because someone is black and you can’t refuse a service because someone is gay. It’s really incredibly simple.
People comparing a wedding cake to asking someone to collaborate in making something offensive need to have a talk with themselves. It’s a wedding cake. Get a grip.
This forum may be a bastion for prejudiced views (down to 17%, quite a minority) but thank goodness society is headed is a completely different direction. Enjoy your Pyrrhic victory.