First, I didn't say this baker only made wedding cakes. I said a baker; I was speaking generically. The Muslim baker I referenced earlier couldn't be forced to bake a same sex wedding cake because he baked bread not cakes.
Second, you don't seem to understand the concept of a protected class. A black baker wouldn't have to bake a cake for the KKK because the KKK isn't part of a protected class.
Third, there are, sadly, still churches that prohibit marriage between whites and blacks on religious grounds. Should a white baker be allowed to refuse to bake a cake for an interracial couple because it violates his beliefs. What if he refused to bake a cake for a Christian bride who was marrying a Muslim man?