> the person who uttered the racist threat is still bound by law and physical violence is not free speech. And here we've found the line to make free-speech work: even-handed law-enforcement against physical violence, theft etc.
It's factually true but I don't think it's realistic. First, much of what people can do won't expose them to law enforcement. They can get you fired, prevent you from getting hired, cost you that contract, keep your kids off the football team or out of the good school, pass laws that make your life difficult, have city inspectors and police go over everything you do with a fine tooth comb (e.g., driving while black), etc. Second, law enforcement and the legal system in general have a long history of not protecting marginalized groups but persecuting them. When the sheriff, mayor, judge, prosecutor, and jury are all white and all know each other, and you know the history of blacks in the legal system, you may not want to trust your fate to their protection.
> Racist slurs on the other hand, while more cutting to people who have been marginalized, are just words designed to produce an emotional response.
Again, this may be true in theory but I strongly disagree it's true in reality. They are serious threats because they have a long, very well-established history of being backed up with action. I don't think you mean it this way, but it amounts to saying (as I understand it) that blacks don't face actual discrimination, therefore the threats are empty.