There have been several recent court cases regarding Christian businesses that have refused to provide service to certain customers based on religious grounds.
Assuming secular law has no opinion (dina demalchuta does not apply), what are the Halachot of a Jewish-owned business refusing to serve certain customers? Is is permitted? Prohibited? Required in certain circumstances? Would it matter if the customer is Jewish?
For example, can\should\must a Jewish-owned florist refuse to provide flowers for a gay wedding (to use the case that's been in the news recently) ?