How could it not be?

of course

you are free to deal with (or refuse to deal with) whoever you like

Yes. This is not how I would personally handle my business affairs but it sends a direct, honest signal from the person sending it (much like actual free markets send clear price signals, whereas our manipulated, corrupt markets send terrible price signals and nobody truly knows the value of things). Just because the state gets to set rules its plebs are forced to follow, it doesn't mean that the rules are inherently correct, just, fair, etc. It simply means that the state is forcing a rule set upon the people it rules over. If the non-whites don't like the hiring practice they don't have to engage with this business. And the opposite is true, if the business said black only candidates, then perhaps whites wouldn't patronize the business. Forcing people to do things they don't want to do only creates anger, it doesn't somehow make people more tolerant or obedient IMHO.