You don't just plop a cake topper on top of a wedding cake. It is part of the design and it gets frosted on.
So I am condoning homosexual behavior when I care for homosexual patients in the hospital as a nurse? Even the Christian hospitals accept patients of all belief systems. I think you are actually showing God's love when you serve the unbelieving with unconditional love. Not making a cake isn't going to stop the wedding....
What if the baker were legally required to provide service no matter what, and some racist group asked for a cake that said, "Kill all the N_____s"? Would you be in favor of baking that cake because of 'love thy neighbor?"
If baking the cake weren't a way of enforcing conformity and agreement with their views, LGBT activists would not make a big deal out of it.