You idea about offensive art is dumb and irrelevant.
The baker has made many cakes for gay weddings, he just does not know it. When he learns he is making a cake for a gay wedding, he is suddenly offended?

Let’s say a wedding planner goes into Jack Philips cake shop and orders an elaborate, custom wedding cake.
It has 10 layers and has a mountain stream of icing cascading down the layers tha t look like mountains. It is stunning. The baker is beyond proud of his work. He accepts payment and the wedding planner takes it away. What a feel good story!

But wait. The wedding planner never told the baker the cake is for a gay wedding. The cake is rolled out at the gay wedding and is eaten, because it is a cake.

Does thst take away from the baker? Is he less proud of his work if he finds out it was in a gay wedding?
Does it make it less of a cake? Is it less of a work of art?

The baker is choosing to be offended. It is immature.