Yes. It is now. Legislation to make it illegal was an act of society deciding that an otherwise-legal business decision was so unpalatable it must be prevented

Yes. It is now. Legislation to make it illegal was an act of society deciding that an otherwise-legal business decision was so unpalatable it must be prevented. -- That's what makes it such a good hypothetical. You can ask yourself "if such business decisions were legal, should they be prevented or discouraged? And what mechanisms would be appropriate?" So I don't understand your point. Yes, it's illegal now. Are you arguing for companies to always operate as they see fit, as long as it's legal, and regardless of moral opinions of anyone other than themselves? Are you arguing that there shouldn't be any moral-based laws to stop discrimination like this one? Are you making a point that companies should be stopped from making immoral decisions with the force of law beyond the current limitations? Are you making a point that the current set of groups legislation gives legal protection perfectly overlaps with the set of groups that that morally should have protection from otherwise-legal business decisions? Are you simply being a pedant about the current boundaries of law without meaningful contribution to clean up the hypothetical or clarify the questions raised by the conversation at hand?