You should be able to refuse to serve anyone for any reason. It's your business.
Now, before you lecture me on the law and the reasons for it, remember I'm old enough to have eaten in places where a sign was posted stating "No Colored people allowed". I objected to that policy then and I do now.
There is also a difference between serving food and performing Holy Matrimony. At least, to me there is.
There is nothing religious about the serving of your food. But we could pretend you are not serving a particular food item that some ethnic group likes to eat. Now they force you to stock that food whether you want to or not. You're discriminating against them by refusing to put boiled cocktoaches on your menu????????
Just how far do we allow government to encroach on our businesses? You better have them roaches ready when I come to visit.