..and he places as order for large cake with the decoration showing a muslim warrior cutting off the head of a jewish rabbi. Underneath are the words, "If you see a Jew, remove his head.' Question. Should the business owner be forced by law to make the muslim that cake? Or can he just refuse the business without being prosecuted by the State?
even better, should a kosher bakery be forced to write "Happy Birthday Jesus, Lord and Savior and King of the Jews", on a cake?
no, its a perfect analogy. asking a Christian to write on a cake "Happy Wedding to Mark and Steve" is the same as asking a Jew to write "happy Birthday to Jesus, Lord & Savior and King of the Jews". Both violate their religious beliefs.
Please read carefully. It's really very simple. There is no justification for still failing to understand and certainly no justification for pretending not to understand to try to make some flawed political point. Discrimination is about the nature of the customer, not the nature of the product. If you make wedding cakes, you can't make them for mixed-sex weddings but refuse for same-sex weddings (you can disagree on the equality of the two but that's not the argument you're trying to make here). Equally, if you made "Religious leader decapitation" cakes for other people, you couldn't refuse to make one for a Muslim customer. If you don't make "Religious leader decapitation" cakes for anyone though, there is obviously no discrimination.
Actually, I have never met a Jew who would take offense at that. They do not accept Jesus as the Messiah, and I have never met any that would find that offensive, they simply do not recognize it as true is all. As a Christian, I would have no problem writing "Happy Birthday Buddha" or "Happy Birthday Abū al-Qāsim Muḥammad - the one true Prophet of the world". After all, why should I? What another believes in no way offects me. Of course, a great many people take offense at anything and anybody that does not agree with them.