Yeah, and if you enslave a black person then there is no “white supremacist crime”. Which leads to the question, perhaps there is something wrong with your libertarian moral reasoning, just like there is something wrong with white supremacist moral reasoning.

Surely the examples I gave were immoral. Certainly private vices are not crimes. However blackmail is not a private vice. Blackmail is immoral, is not private, and is calculated to effect someone else. It does not have the attributes used to argue for the non-criminality of vices ala Lysander Spooner.

Negative rights, the ones normally enshrined by libertarians, are all about being left alone by others. A blackmailer is certainly violating a principle of leaving others alone when he coerces his victim. He violates the right of the victim by imposing a objectionable choice on him that unjustly takes his work product, without providing anything the blackmailer created on his own.

A) Witness to a crime should not be able to take payment from a criminal to keep quite about it. By approaching the criminal with a blackmail offer his is showing a guilty mind, mens rea, that he is willing to participate in the cover up of a crime.

Well, even if you are right, this is because in this case there is a duty to testify as to a crime committed. It would not establish that blackmail per se is a crime. Only that you have a duty to testify if you witness a crime and to fail to do this is itself a crime.

But is it? Why do I owe a duty to testify, to report what I saw? If I’m the victim, don’t I have the right to forgive the crime? (what else is settlement of my claims for some kind of restitutionary payment but a forgiveness of the crime?) And if I’m some third party, to whom do I owe the duty-to-testify? The victim? Why? I have no contract with him.

I agree, I have an obligation not to falsely accuse someone of a crime, since this could play a causal role in others harming the accused. (See my Causation paper for more on this.) In this case you are playing a causal role in aggression. But in blackmail, where you are telling the truth about someone, you are at most playing a causal role in third parties doing what is within their rights. It is similar to the reason why defamation should not be a tort or crime: your reputation is what others think of you and they have a perfect right to change their opinion of you even if they do so based on lies told by others. IT’s up to them to choose what to think and why to think it.

B) Parents adopt a child whose biological parents were criminal, or rejected the child. Parent wishes to keep this secret till child is mature enough to handle emotionally (or forever.) Also adoptive parent may be protecting the child from retribution by someone the biological parent hurt.

Blackmailer learns this private information and threatens to damage adoptive child’s life unless paid money. In other words the blackmailer has coerced money out of the parent in return for the treat of damaging the child. Money the blackmailer had no part in earning.

“Damaging” is vague. Libertarianism only “counts” “damage” or “harm” as something that is a rights violation, if it is aggression. So you need to show why the spilling of the secret violates the rights of the child. You can’t just point to “harm” or “damage”–after all if I build a dry cleaner across from yours I make take business away from and “harm” you but this is not a problem (this is one reason I critiqued one libertarian book that focused on “harm” (Patrick Burke’s “No Harm”–see my review); and why J.C. Lester’s is also problematic in talking of “imposing costs” (see Gordon’s review).

By approaching the parent the blackmailer shows an guilty mind, mens rea, to harm the child since he is willing to take resources away the parent which is supporting the child, or to divulge information that would harm the child.

This is floppy, imprecise, vague talk. The question is: are you committing aggression, or at least acting so as to play a causal role in the commission of aggression? If not, no libertarian crime.

Simple examples.
A) Witness to a crime should not be able to take payment from a criminal to keep quite about it.
B) Parents adopt a child whose biological parents were criminal, or rejected the child. Parent wishes to keep this secret till child is mature enough to handle emotionally (or forever.) Also adoptive parent may be protecting the child from retribution by someone the biological parent hurt.

Blackmailer learns this private information and threatens to damage adoptive child’s life unless paid money. In other words the blackmailer has coerced money out of the parent in return for the treat of damaging the child. Money the blackmailer had no part in earning.