Should the few Christians who still go around saying “The Jews killed Jesus” be able to refuse a cake or any other service to Jewish people, be they even Reform Jews who have no problem going into non-Jewish stores for any kind of service?
No, as that was not my argument, which you should be dealing with rather than a strawman.
The issue is not about refusing service to anyone based upon religion, race, country etc., but refusing to make a special work for or otherwise accommodate a certain event with a substantial moral weight that the owner finds morally contrary to his known beliefs, along as such accommodation was not for essential services, such as the need for shelter which was not available elsewhere.
Thus a Muslim baker could refuse to make a cake for celebration of the birth of the nation of Israel, but could not refuse any service simply because of their religion.