Well such a person would be guilty of harassing the individual personally - which is an arrestable offence. But should someone be allowed to appear in public and call black people that? Yes. Because the alternative is a world of double standards. After all, there seems to be no restriction on the number of people who are allowed to go on TV and in the media and talk about how white males/white people are the root cause of all problems and to demonise them endlessly.