Isn't baking a cake subject to WHAT it's for not WHO it's for? Why couldn't they make that argument as the owners were willing to bake them a cake for something else other than a same sex wedding? For example, I'm assuming they would also deny to make a cake that was pro abortion, alcoholism, witchcraft, etc. I don't think it would then be considered discrimination if they looked at the WHAT instead of the WHO.
You make a good point. You could be a lawyer