In a free society, all exchanges of goods and services, and associations are voluntary.  Involuntary exchanges in such a society are illegal. I don't have the moral authority to forcibly interfere with the aforementioned voluntary exchanges and associations.  Neither do the rest of you. Having the govt. do it for us makes it no more moral.  "Open to the public" is not synonymous with "owned by the public." The invented notion of "public accommodations" was a taking of property rights (as harsh as that sounds).

Personally, I would have sold the dudes (who I believe were fishing for a fight) a cake with 2 dudes on it.  That's my choice to make. The baker didn't have wedding cakes with 2 dudes on them on his menu.  Refer back to my first sentence in the paragraph above (though without a doubt, we're not an entirely free society.  We could be if at least 87% of people weren't some degree of busy body control freak).