So, hiring someone to photograph something is different than hiring someone to bake something?
Purchasing a commodity =/= hiring someone for a service.
(not that discrimination should be given free rein in the latter case either, but there's a bit more nuance there)
When one is buying a cake, you are both purchasing the commodity of the cake and the service of making the cake.
When one is buying photographs, you are both purchasing the commodity of the cake and the service of taking the photographs.
They're not completely similar, but at least to me there's not much nuance there.
TL;DR: I would rather be discriminated against than have someone do something for me he doesn't want to do.