Pretty much everyone agrees that a private person be able to pick friends free from interference. I see a lively argument going about the right to give or refuse business free of interference as well. Let me postulate these hypothetical situations:
A person runs a business — retail or consulting or some other, doesn’t really matter — and feels that a particular customer is unwelcome. Should they be forced to serve that customer? The reluctance could be based on credit history, political disagreement, just a hunch that the customer will cause trouble. Yes or no?
If you say yes, the person should be forced to do business with everyone, would you still hold the same view if the customer is Lon Horiuchi? The Grand Dragon of the Ku Klux Klan? Someone else that you and the proprietor both hold reprehensible?
Businesses already legally discriminate by age, even though that’s a characteristic over which people have no control. If discrimination by sex, ethnicity, religion, sexual orientation, political affiliation, plain personal dislike are all to be illegal, why should discrimination by age or citizenship or any other factor remain legal?