I am not sure why you pick on blackmail specifically. Most of your points apply to many kinds of human interactions. The original reason for some specific actions being made illegal is based on consequentialism, to convert utilitarian reasons into deontological ones, and, after a time, into virtue-ethical. Not all high negative utility actions get outlawed, and many positive utility actions get outlawed for other reasons, but the general pattern persists. Changes in society eventually result in changes in laws. What used to be illegal becomes legal and vice versa, generally based on the amount of real or perceived harm it causes. When copying became trivial, copyright laws grew teeth. Once same sex is no longer an emotional horror, it is no longer outlawed. If one day human life becomes cheap again (like it is now in some places), murder will eventually become legal and accepted. To productively discuss blackmail’s legality one would need to evaluate the actual, not imagined or edge-cases harm it causes in the context of other activities, legal and illegal, and see where it fits on the utility scatter plot. If you find it to be broadly among the cloud of illegal activities, then you have a case for it being made illegal. If it is on the margins between legal and illegal, then you don’t have a case. That’s it.
I am not sure why you pick on blackmail specifically. Most of your points apply to many kinds of human interactions. The original reason for some specific actions being made illegal is based on consequentialism, to convert utilitarian reasons into deontological ones, and, after a time, into virtue-ethical. Not all high negative utility actions get outlawed, and many positive utility actions get outlawed for other reasons, but the general pattern persists. Changes in society eventually result in changes in laws. What used to be illegal becomes legal and vice versa, generally based on the amount of real or perceived harm it causes. When copying became trivial, copyright laws grew teeth. Once same sex is no longer an emotional horror, it is no longer outlawed. If one day human life becomes cheap again (like it is now in some places), murder will eventually become legal and accepted. To productively discuss blackmail’s legality one would need to evaluate the actual, not imagined or edge-cases harm it causes in the context of other activities, legal and illegal, and see where it fits on the utility scatter plot. If you find it to be broadly among the cloud of illegal activities, then you have a case for it being made illegal. If it is on the margins between legal and illegal, then you don’t have a case. That’s it.
This is in response to other writers, esp. Robin Hanson. That’s why.