To what end? Say that they tell me that they hate my kind, now what? Am I allowed to mail them because they’re a bigot? I expect you would say no to that. So then, to what end? So I can ban them from my private property?
If someone is prone to racist remarks that should be noticed and their thought process/moral failings should be addressed. If you simply threaten reprisal in advance you not only don’t address their core issue, but you also hide it from sight!