If it's the person's private property, doesn't he have the right to sell (or not to sell) to whomever he chooses?
If someone wants to stand up and loudly announce that they're a racist, who are we to stop them?
I agree with you, see my reply #76. The problem however arises when the offending party does not "stand up and loudly announce that they're a racist," until after the damage is done. If prior notice of intended sale restriction is made on an equal basis with the notice of intent to sell, and done so in a manner as to adequately guide denied potential buyers to move on without stopping to inquire, then I would agree that "he should be able to sell to whomever he pleases."