I think this is more like businesses are not obligated to make or do everything for customers. They can't discriminate, but they don't have to provide everything for everyone. This baker is obviously running a Christian bakery, and so only makes Christian products. He does not have to make non-Christian things. He can't refuse to sell someone a cake based on gender, sex, religion, etc, but he doesn't have to make anything they want. It's like if you had a black history book shop, it would not be illegal to not have European history books. A business is allowed to make, and sell only what they want.